ArticlePDF Available

Abstract and Figures

Widespread mortality of intertidal biota was observed following the 7.8 Mw Kaikoura earthquake in November 2016. To understand drivers of change and recovery in nearshore ecosystems, we quantified the variation in relative sea-level changes caused by tectonic uplift and evaluated their relationships with ecological impacts with a view to establishing the minimum threshold and overall extent of the major effects on rocky shores. Vertical displacement of contiguous 50 m shoreline sections was assessed using comparable LiDAR data to address initial and potential ongoing change across a 100 km study area. Co-seismic uplift accounted for the majority of relative sea-level change at most locations. Only small changes were detected beyond the initial earthquake event, but they included the weathering of reef platforms and accumulation of mobile gravels that continue to shape the coast. Intertidal vegetation losses were evident in equivalent intertidal zones at all uplifted sites despite considerable variation in the vertical displacement they experienced. Nine of ten uplifted sites suffered severe (>80%) loss in habitat-forming algae and included the lowest uplift values (0.6 m). These results show a functional threshold of c.1/4 of the tidal range above which major impacts were sustained. Evidently, compensatory recovery has not occurred—but more notably, previously subtidal algae that were uplifted into the low intertidal zone where they ought to persist (but did not) suggests additional post-disturbance adversities that have contributed to the overall effect. Continuing research will investigate differences in recovery trajectories across the affected area to identify factors and processes that will lead to the regeneration of ecosystems and resources.
Content may be subject to copyright.
GeoHazards
Article
Threshold Effects of Relative Sea-Level Change in Intertidal
Ecosystems: Empirical Evidence from Earthquake-Induced
Uplift on a Rocky Coast
Shane Orchard 1, 2, * , Hallie S. Fischman 1, Shawn Gerrity 1, Tommaso Alestra 1, Robyn Dunmore 3
and David R. Schiel 1


Citation: Orchard, S.; Fischman, H.S.;
Gerrity, S.; Alestra, T.; Dunmore, R.;
Schiel, D.R. Threshold Effects of
Relative Sea-Level Change in
Intertidal Ecosystems: Empirical
Evidence from Earthquake-Induced
Uplift on a Rocky Coast. GeoHazards
2021,2, 302–320. https://doi.org/
10.3390/geohazards2040016
Academic Editor: Robert Kayen
Received: 9 August 2021
Accepted: 24 September 2021
Published: 29 September 2021
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1Marine Ecology Research Group, University of Canterbury, Private Bag 4800,
Christchurch 8140, New Zealand; halliefischman@ufl.edu (H.S.F.); shawn.gerrity@canterbury.ac.nz (S.G.);
tommaso.alestra@canterbury.ac.nz (T.A.); david.schiel@canterbury.ac.nz (D.R.S.)
2School of Earth and Environment, University of Canterbury, Private Bag 4800,
Christchurch 8140, New Zealand
3Cawthron Institute, 98 Halifax Street, Nelson 7010, New Zealand; robyn.dunmore@cawthron.org.nz
*Correspondence: s.orchard@waterlink.nz
Abstract:
Widespread mortality of intertidal biota was observed following the 7.8 Mw Kaik
¯
oura
earthquake in November 2016. To understand drivers of change and recovery in nearshore ecosys-
tems, we quantified the variation in relative sea-level changes caused by tectonic uplift and evaluated
their relationships with ecological impacts with a view to establishing the minimum threshold and
overall extent of the major effects on rocky shores. Vertical displacement of contiguous 50 m shoreline
sections was assessed using comparable LiDAR data to address initial and potential ongoing change
across a 100 km study area. Co-seismic uplift accounted for the majority of relative sea-level change
at most locations. Only small changes were detected beyond the initial earthquake event, but they
included the weathering of reef platforms and accumulation of mobile gravels that continue to shape
the coast. Intertidal vegetation losses were evident in equivalent intertidal zones at all uplifted sites
despite considerable variation in the vertical displacement they experienced. Nine of ten uplifted
sites suffered severe (>80%) loss in habitat-forming algae and included the lowest uplift values
(0.6 m). These results show a functional threshold of c.1/4 of the tidal range above which major
impacts were sustained. Evidently, compensatory recovery has not occurred—but more notably,
previously subtidal algae that were uplifted into the low intertidal zone where they ought to persist
(but did not) suggests additional post-disturbance adversities that have contributed to the overall
effect. Continuing research will investigate differences in recovery trajectories across the affected
area to identify factors and processes that will lead to the regeneration of ecosystems and resources.
Keywords:
natural hazards; seismic displacement; post-disaster planning; hydro-ecology;
relative
sea-level; tipping points; impact assessment; multiple stressors; social-ecological system; New Zealand
1. Introduction
Relative sea-level trends are pervasive drivers of change in nearshore coastal systems
due to the multitude of social and ecological relationships that are structured by the
position of land in relation to the sea [
1
]. Enduring sea-level changes present a specific set
of challenges that differ from those associated with periodic extreme events. For example,
they are more likely to force long-term adjustments to the spatial configuration of coastal
landscapes upon which both periodic extreme events and regular hydrological fluctuations
interact [
2
]. Land-mass displacement mechanisms play a critical role in determining relative
sea-level trends and include crustal movements associated with tectonic plates and isostatic
responses to stress redistribution associated with glacial de-loading [
3
,
4
]. Land surface
elevation changes may also result from shallow sources of uplift and subsidence such as the
GeoHazards 2021,2, 302–320. https://doi.org/10.3390/geohazards2040016 https://www.mdpi.com/journal/geohazards
GeoHazards 2021,2303
movement of hydrocarbons and groundwater, decay of organic material and compaction
of sediments [57].
Rapid changes in relative sea-levels can result in widespread disturbance to the an-
tecedent pattern of development in both natural and anthropogenic environments. While
various degrees of resistance or resilience to these changes are a feature of social–ecological
systems, there are also tipping points beyond which major losses are sustained
[810]
.
These thresholds are therefore of fundamental interest for the study of disaster risk reduc-
tion and disaster recovery processes to improve strategic planning and preparedness for
further change. The potential for rapid displacement events is a serious consideration in
seismically active regions that include vast tracts of coastline in territories close to sub-
duction zones in the Pacific Ocean [
11
]. In addition to the direct impacts of hydrological
changes, the cumulative effects of land mass movements have important consequences
for the development of climate-change adaptation strategies [
12
,
13
]. Depending on the
direction of motion, they may potentially mitigate or exacerbate eustatic sea-level rise
effects and drive additional interactions with erosion and sedimentation processes [
14
16
].
There are few contemporary studies of the impact of co-seismic displacement events on
coastal communities, but they have undoubtedly been a regular occurrence over geological
time periods. The available studies have documented massive changes in the structure and
function of coastal ecosystems with associated impacts on the persistence and condition
of natural resources, including shellfish and finfish fisheries, coastal forests, blue-carbon
ecosystems, and coastal land. Recent examples include a 2007 earthquake in the Solomon
Islands that caused subsidence leading to major changes in the spatial extent of mangroves
and coastal wetlands [
17
]. In New Zealand, the 2010–2011 Canterbury earthquakes caused
both subsidence and uplift in coastal waterways as a consequence of tilt effects associated
with fault-line movements [
18
]. Ground-surface deformation caused widespread damage to
residential properties in low-lying areas, and exacerbated flood risk in areas of subsidence
leading to a managed retreat initiative [
19
21
]. Hydrological changes also caused the loss
of coastal wetlands and shorebird habitat in areas of relative sea-level rise as characteristic
ecosystems moved landward [
2
,
12
,
22
]. In uplifted areas, impacts included shifts in the salt
water intrusion characteristics of lowland waterways leading to the downstream migration
of coastal zonation patterns and key habitats [23,24].
In the 2010 8.8 Mw Chilean earthquake, coastal uplift was associated with severe
losses of low intertidal sand beach habitat and gains in upper- and mid-intertidal habi-
tat [
25
,
26
]. These impacts were influenced by the magnitude and direction of vertical
displacement, interactions with substrate types, and the mobility of characteristic biota [
25
].
Similar circumstances are found in the present study, which investigates impacts of the
2016 7.8 Mw Kaik¯
oura earthquake on the east coast of New Zealand. The associated fault
ruptures were among the most complex ever recorded [
27
29
] and manifested as a highly
variable pattern of ground-level displacement but mostly in the direction of uplift [
30
].
These physical impacts led to widespread reassembly of ecological communities on rocky
shorelines
[3133]
. Associated social and economic effects included new landscape configu-
rations altering access to the coast, and the closure of commercial fisheries and recreational
harvesting of seaweeds and shellfish [34,35].
Objectives
In the aftermath of the earthquake we began a research programme to determine the
severity of impacts and investigate prospects for recovery. In this study, our major objectives
were (a) to quantify relative sea-level changes caused by the earthquake as close as possible
to our post-earthquake study sites in the new intertidal environment, and (b) to estimate the
severity of impacts on major habitat-forming macroalgal, particularly large brown kelp and
fucoid algae (phaeophyceae) that provide habitat, are highly productive, support a large
biomass, and define ecosystem structure on the rocky shores of this coast [
36
]. Challenges
for this assessment included the availability of elevation data within the landforms and
ecosystem types of interest, particularly in the new intertidal areas that were previously
GeoHazards 2021,2304
submerged and therefore outside of the spatial extent of aerial and satellite-based altimetry
surveys. There was also a need to include the evaluation of tilt effects that could lead
to ground-level displacement gradients across the shore profile, and the potential for
continued displacement subsequent to the main seismic event.
Despite being an investigative study of a natural event, we identified several intriguing
hypotheses, including the expectation that the short dispersal distances of reproductive
large brown algae [
37
,
38
] would limit recruitment into areas of newly available habitat,
reducing the potential for recovery of impacted population and/or slowing recovery rates.
Interactions with other stressors (e.g., erosion, compromised light environment) in the
post-quake environment were also expected to limit the potential for recovery through
rapid post-quake recruitment and potentially reduce the survival of individuals that were
uplifted to new and more physically stressful vertical positions within the tidal range. We
expected that testing these hypotheses would manifest as net losses in habitat-forming
algae for equivalent pre- and post-quake tidal zones, which are the focus of this study.
Note that these expectations contrast with an alternative hypothesis in which charac-
teristic habitats remain intact due to the survival of key species and/or rapid recovery from
recruitment, with the overall intertidal zone simply shifting along the coastal profile in
response to new sea levels. In considering the implications, the latter is associated with few
negative impacts or quick recovery through seeding from nearby reproductive individuals
that survived initial impacts. In contrast, the former are indicative of widespread ecosystem
collapse with associated social and economic impacts, such as prolonged fishery closures
and other ecosystem service losses.
2. Materials and Methods
2.1. Study Area
The study area is a contiguous 100 km section of coastline stretching from Oaro to
Waipapa Bay on the east coast of the South Island of New Zealand. Kaik
¯
oura is a small town
(population c.2500) located at the base of the Kaik
¯
oura Peninsula, a prominent feature on
this wave-exposed coast (Figure 1). The coastal environment of this area is renowned for its
rocky shore habitats that support a rich diversity of intertidal and shallow subtidal marine
species, including habitat-dominating seaweeds, understory species, rock lobsters, New
Zealand abalone (p
¯
aua), and other invertebrates [
33
,
39
]. The area features a wide variety
of substrate types and topographies, including near-horizontal platforms and extensive
rock and boulder fields, interspersed with dynamic mixed sand-gravel and sandy beaches.
Much of the coast is sparsely populated and the single highway along it was severely
damaged and closed for over a year. As a result, access to study sites had many logistical
constraints, especially in the early phases of the study.
2.2. Data
Our overall approach took advantage of the availability of light detection and ranging
(LiDAR) datasets that included three post-quake LiDAR acquisitions and a comparable pre-
quake dataset (Table 1). The two immediate post-quake datasets (covering different spatial
extents) were combined and all data re-projected to a common reference system and aligned
to facilitate vertical displacement analyses based on differencing of 1
×
1 m digital elevation
models (DEM). To evaluate temporal effects, we compared differences derived from the
pre-quake (July 2012) to immediate post-quake (December 2016) period, and the immediate
post-quake to 18-months post-quake (June 2018) LiDAR datasets. Confounding factors
from ground-level changes between the July 2012 LiDAR acquisition and the earthquake
event have been reviewed in previous studies [
30
], and the most significant seismic event
in that period was associated with the Cook Strait earthquake sequence of up to Mw 6.6
that produced only small vertical displacements (<5 mm) in the Kaik
¯
oura region [
40
]. The
potential for further post-seismic movement has been also assessed in previous work using
interferometric synthetic aperture radar (InSAR) and GPS data that showed considerable
further displacement effects at many sites in the upper South Island and much farther
GeoHazards 2021,2305
afield in the lower North Island [
41
,
42
]. Other sources of variance affecting differencing
analyses include erosion and accretion effects that are difficult to account for in the before–
after earthquake comparison. However, we made use of high resolution (0.1 m) RGB
imagery captured during the aerial LiDAR acquisition to identify deposition from rockfall,
unstable surfaces such as riverbeds, and anthropogenic modifications such as earthworks
associated with earthquake recovery activities on the road and rail corridor. These areas
were manually delineated where visible in the aerial imagery and the DEMs masked to
remove these features from the analysis.
GeoHazards 2021, 2, x FOR PEER REVIEW 4 of 20
Figure 1. Location of the study area on the east coast of the South Island of New Zealand.
2.2. Data
Our overall approach took advantage of the availability of light detection and rang-
ing (LiDAR) datasets that included three post-quake LiDAR acquisitions and a compara-
ble pre-quake dataset (Table 1). The two immediate post-quake datasets (covering differ-
ent spatial extents) were combined and all data re-projected to a common reference system
and aligned to facilitate vertical displacement analyses based on differencing of 1 × 1 m
digital elevation models (DEM). To evaluate temporal effects, we compared differences
derived from the pre-quake (July 2012) to immediate post-quake (December 2016) period,
and the immediate post-quake to 18-months post-quake (June 2018) LiDAR datasets. Con-
founding factors from ground-level changes between the July 2012 LiDAR acquisition and
the earthquake event have been reviewed in previous studies [30], and the most signifi-
cant seismic event in that period was associated with the Cook Strait earthquake sequence
of up to Mw 6.6 that produced only small vertical displacements (<5 mm) in the Kaikōura
region [40]. The potential for further post-seismic movement has been also assessed in
previous work using interferometric synthetic aperture radar (InSAR) and GPS data that
showed considerable further displacement effects at many sites in the upper South Island
and much farther afield in the lower North Island [41,42]. Other sources of variance af-
fecting differencing analyses include erosion and accretion effects that are difficult to ac-
count for in the beforeafter earthquake comparison. However, we made use of high res-
olution (0.1 m) RGB imagery captured during the aerial LiDAR acquisition to identify
deposition from rockfall, unstable surfaces such as riverbeds, and anthropogenic modifi-
cations such as earthworks associated with earthquake recovery activities on the road and
rail corridor. These areas were manually delineated where visible in the aerial imagery
and the DEMs masked to remove these features from the analysis.
Figure 1. Location of the study area on the east coast of the South Island of New Zealand.
Table 1. LiDAR data specifications.
Timing in
Earthquake
Sequence
LiDAR
Acquisition
Date
Supplier Commissioning Agency
Accuracy
Specification (m)
Vertical Horizontal
pre-earthquake Jul 2012
Aerial Surveys Ltd.
Environment Canterbury unknown unknown
immediate
post-quake Nov 2016 AAM NZ Ltd.
New Zealand Transport Agency
±0.10 ±0.50
Immediate
post-quake Dec 2016–Jan 2017 New Zealand
Aerial Mapping
Land Information New Zealand
±0.10 ±0.50
18 months
post-quake Jun 2018 AAM NZ Ltd.
Land Information New Zealand
±0.10 ±0.50
2012 LiDAR data were originally provided in New Zealand Vertical Datum (NZVD) 2009 but were reprocessed by Aerial Surveys Ltd. to
NZVD2016 and subjected to control checks.
GeoHazards 2021,2306
2.3. Vertical Displacement
To assess spatio–temporal variability in vertical displacement at the coast, we con-
structed an assessment baseline using the first contiguous 0.1 m contour common to all
datasets, which was located at the approximate position of the 2012 (pre-quake) mean
high water springs (MHWS). A set of analysis windows was constructed landward of this
baseline to facilitate the closest possible approximation of ground-level change within new
intertidal areas (generally located seaward of this line), which are a key focus for recovery
and impact assessments (Figure 2A). Tilt effects were assessed independently (see below)
to verify the transferability of these measurement to the new intertidal zone. At Waipapa,
a sizeable portion of the intertidal zone was lifted higher than surrounding areas to land-
ward as the result of block-faulting on the western strand of the Papatea Fault (Figure 3A).
Fortunately, outcrops of relatively tall flat-topped rocks are a characteristic of this area and
were captured in both pre- and post-earthquake LiDAR data. This enabled the calculation
of uplift values for the uplifted block to be calculated using manually constructed analysis
windows (Figure 2B).
Ground-level changes were computed by differencing the DEMs after applying slope
constraints (see below) and summarised using zonal analysis of returns within each of the
analysis polygons. Vertical displacements recorded in national geodetic updates to the Land
Information New Zealand (LINZ) survey benchmark network were also catalogued for
comparison to the values obtained. To assess the interactions between vertical displacement
and substrate, four substrate types (rocky reef, boulder, mixed sand–gravel and sandy
beach) were mapped at the position of the new (post-quake) MHWS corresponding to
the 0.5 m NZVD contour using 2018 aerial imagery and ground-truthing in the field.
Each analysis window was classified according to substrate type in the adjacent coastal
environment by intersecting the substrate map with its associated shore-perpendicular
transect (Figure 2).
2.4. Tilt and Horizontal Displacement Effects
To test for tilt effects in the vicinity of the coast, three sets of analysis windows (each
n= 2000
) were constructed with different landward extents (50 m, 200 m and
500 m
) ori-
ented perpendicular to each 50 m segment of the baseline (Figure 2). Horizontal ground
displacement effects that confound the measurement of vertical displacement using over-
lapping DEMs were controlled by restricting the analysis domain to nearly flat ground
(Figure 3). Two separate slope thresholds (less than 2 and 5 degrees, respectively) were
calculated by slope analysis of the DEMs and applied as masks to the differencing analysis.
Results from the above analyses were used to provide sensitivity tests of tilt and
horizontal displacement effects on the vertical differencing assessment. One way ANOVAs
were used to test for significant differences in vertical displacement for the independent
variables of orthogonal distance from the coast (tilt effects) and slope constraints (horizontal
displacement effects). Linear regressions were also used to further test for biases across the
range of uplift values found within the sampling domain for each of the above comparisons.
2.5. Field Surveys
Quadrat-based field surveys were used to assess biological impacts within the in-
tertidal area at 12 sites (Table 2). In these surveys, transects of 30–50 m were laid out
horizontally along the shore at different tidal heights (see below) representing equivalent
mid and low intertidal zones, respectively, and ten 1 m
2
quadrats sampled from each zone
and the percentage cover or abundance of key species recorded, including all visible algae
and invertebrates. These sites were selected to provide both geographical coverage and
representation of a range of uplift values across the extensive study area. Their locations
also reflect a paired sampling strategy whereby six pairs of sites were located in areas
of similar uplift. The most southern sites were located at Oaro, which had experienced
negligible uplift and therefore functioned as a control (Table 2). The remaining sites in-
cluded two sites at Omihi, four sites on Kaik
¯
oura Peninsula, and four sites in higher uplift
GeoHazards 2021,2307
zones in the north of the study area (Figure 1). All of these sites are rocky shorelines that
were previously dominated by large brown algae with a similar composition of rocky reef
substrate types (e.g., reef and boulder) in pre- and post-earthquake intertidal areas.
GeoHazards 2021, 2, x FOR PEER REVIEW 6 of 20
Figure 2. (A) Sampling setup for differencing analysis of 1 × 1 m digital elevation models derived from LiDAR data show-
ing sampling origin points at 50 m spacing on an assessment baseline located at the approximate position of the pre-
earthquake mean high water springs. 50 × 50 m analysis windows landward of this line are within the spatial extent of all
LiDAR datasets. Shore-perpendicular transects extending seaward were used to associate each analysis window with the
dominant substrate type in the adjacent intertidal area. Two of the field survey sites (Waipapa North and Waipapa La-
goon) are located in the inset. (B) Manually constrained analysis windows used to assess uplift at the Waipapa sites where
block-faulting uplifted intertidal areas higher than was recorded in the analysis windows to landward on the assessment
baseline. The underlying image is a difference model with the same uplift scale as (A) for the pre-quakeimmediate post-
quake period.
Figure 2.
(
A
) Sampling setup for differencing analysis of 1
×
1 m digital elevation models derived from LiDAR data
showing sampling origin points at 50 m spacing on an assessment baseline located at the approximate position of the
pre-earthquake mean high water springs. 50
×
50 m analysis windows landward of this line are within the spatial extent of
all LiDAR datasets. Shore-perpendicular transects extending seaward were used to associate each analysis window with the
dominant substrate type in the adjacent intertidal area. Two of the field survey sites (Waipapa North and Waipapa Lagoon) are
located in the inset. (
B
) Manually constrained analysis windows used to assess uplift at the Waipapa sites where block-faulting
GeoHazards 2021,2308
uplifted intertidal areas higher than was recorded in the analysis windows to landward on the assessment baseline. The
underlying image is a difference model with the same uplift scale as (
A
) for the pre-quake—immediate post-quake period.
GeoHazards 2021, 2, x FOR PEER REVIEW 7 of 20
Figure 3. Workflow for differencing analyses. (A) Aerial image captured concurrent with LiDAR data showing examples
of surface deformation features associated with the earthquake. The acquisition date was November 2016 (immediate post-
quake). (B) 1 × 1 m digital elevation model constructed from LiDAR data at the same date. (C) Example of slope mask
used to constrain the analysis domain to slopes <5 degrees. (D) Example of differencing result for July 2012 and December
2016 ground heights, with the former subtracted from the latter.
2.4. Tilt and Horizontal Displacement Effects
To test for tilt effects in the vicinity of the coast, three sets of analysis windows (each
n = 2000) were constructed with different landward extents (50 m, 200 m and 500 m) ori-
ented perpendicular to each 50 m segment of the baseline (Figure 2). Horizontal ground
displacement effects that confound the measurement of vertical displacement using over-
lapping DEMs were controlled by restricting the analysis domain to nearly flat ground
(Figure 3). Two separate slope thresholds (less than 2 and 5 degrees, respectively) were
calculated by slope analysis of the DEMs and applied as masks to the differencing analy-
sis.
Results from the above analyses were used to provide sensitivity tests of tilt and hor-
izontal displacement effects on the vertical differencing assessment. One way ANOVAs
were used to test for significant differences in vertical displacement for the independent
variables of orthogonal distance from the coast (tilt effects) and slope constraints (hori-
zontal displacement effects). Linear regressions were also used to further test for biases
across the range of uplift values found within the sampling domain for each of the above
comparisons.
Figure 3.
Workflow for differencing analyses. (
A
) Aerial image captured concurrent with LiDAR data showing examples
of surface deformation features associated with the earthquake. The acquisition date was November 2016 (immediate
post-quake). (
B
) 1
×
1 m digital elevation model constructed from LiDAR data at the same date. (
C
) Example of slope mask
used to constrain the analysis domain to slopes <5 degrees. (
D
) Example of differencing result for July 2012 and December
2016 ground heights, with the former subtracted from the latter.
The first round of surveys was completed immediately after the earthquake and
assessed the pre-earthquake intertidal zone in which the majority of species were still
identifiable for at least two months after the earthquake before ‘burning off’ in the post-
earthquake configurations. It is important to note that these initial surveys and selection of
sites were completed in extremely arduous circumstances in a high-hazard environment
with the sites being accessed by combinations of helicopter and on foot. Coastal roads were
impassable due to massive landslides and ongoing rockfall hazard. The strategic priority
for these surveys was obtaining quantitative data representative of pre-quake intertidal
conditions from each general locality, followed by the establishment of additional study
sites where possible. In three locations (Waipapa, Omihi and Sharks Tooth) only single
sites could be surveyed, but these represent the only pre-quake information available
(Table 2). Subsequent survey rounds were completed annually at all sites, and these
sampled the new post-earthquake intertidal area. As a consequence of variable uplift,
there is also variability in the degree of overlap between the intertidal zone in its pre- and
post-earthquake configuration between sites. Due to variable mortality rates, species that
GeoHazards 2021,2309
persisted could be recorded in the post-quake survey areas albeit in a different region of
the intertidal zone, and the overall composition of those zones was in a state of constant
readjustment. To address these aspects, our analysis has a specific focus on the cover and
abundance of key species in equivalent intertidal zones in their pre- and post-earthquake
quake configurations. Post-quake data represent the mean values recorded across all
quadrats for each of three surveys completed in the period 2017–2018, which are compared
to their pre-quake equivalents. This provides the most intuitive and practical means for
empirical evaluation of impacts that are attributable to the earthquake.
Table 2.
Characteristics of study sites showing their pre-earthquake algal cover. The mean percentage cover of four algal
classes (brown, red, corallines, green) was recorded (species by species and then grouped) in 1 m
2
quadrats sampled at
random positions throughout the algal-dominated mid and low intertidal zones. The total cover value can sum to > 100%
due to layering and overlapping of algal species.
Site Coordinates (WGS84) Pre-Earthquake Mean Percentage Cover (%)
X Y Brown Red Coralline Green Total Algae Bare Ground
Oaro South 173.5054366 42.5226367 40 26 63 2.1 131 14
Oaro North 173.5080324 42.5165183 44 28 55 6.8 134 16
Shark Tooth North * 173.6914398 42.4356525 22 4.7 53 0.5 80 20
Shark Tooth South 173.690683 42.4328186 22 4.7 53 0.5 80 20
First Bay 173.7159516 42.4251374 66 3.6 78 0.1 148 7
Wairepo 173.7119037 42.4200986 56 2.2 39 0.0 97 3
Omihi North 173.5250354 42.4885951 41 11 71 0.1 123 7
Omihi South * 173.5225126 42.4926815 41 11 71 0.1 123 7
¯
Okiwi North 173.8709615 42.2174891 77 8.9 60 0.3 147 1
Waipapa South * 173.877159 42.2096143 49 15 73 0.3 138 10
Waipapa Lagoon 173.8775657 42.2045148 49 15 73 0.3 138 10
Waipapa North * 173.8779818 42.2032321 49 15 73 0.3 138 10
* algal cover estimated from nearby sites.
Cover changes in habitat-forming macroalgae were calculated in terms of percentage
gain or loss in canopy cover from their pre-earthquake values. Data were collected for
each species, but the major classes were grouped to give an assessment of major functional
changes. In this assessment, our main focus was large brown algae that include the major
habitat-forming foundation species of this coastal area. Large brown species consisted of
fucoids, including the large southern bull kelp Durvillaea spp., the sea wrack Carpophyllum
maschalocarpum, and Cystophora spp. in the low tidal zone and bladder alga Hormosira
banksii that formed extensive beds in the mid-tidal zone of some sites. The high-tide zone
has no large algae and was omitted from this analysis.
Earthquake impacts were classified as severe (>80% loss), high (51–80%), moderate
(21–80%), or low (1–20%), and a fifth class (nil or gain) was used to show increases versus
pre-quake values. Uplift values derived from the analysis window closest to the field
survey site were used to identify relationships with biological impacts. The extent of major
losses in habitat-forming algae across the whole coast was estimated by identifying the
minimum relative sea-level change associated with high or severe impacts as observed at
the field study sites. The length of coastline with relative sea-level changes exceeding this
threshold was calculated at 50 m intervals for substrates supporting these communities
(rocky reef and boulder) across the 100 km study area.
2.6. Assumptions and Limitations
Key assumptions in this approach include the representativeness of the pre-quake val-
ues obtained since they may be prone to confounding effects, such as seasonal fluctuations,
that can affect estimates of ephemeral algal species, such as the green algae Ulva spp. These
limitations are addressed by the use of the impact classification system that places the
observed gains and losses into broad categories that summarise the predominant pattern.
All of the pre-earthquake percentage cover scores were also checked against long-term
records of similar quadrat-based surveys completed by our research group in the vicinity
of the sites chosen for this assessment. At most sites these include multi-year studies using
GeoHazards 2021,2310
similar quadrat techniques and sampling arrangements [
36
]. It is important to note that the
identification of appropriate control sites (Oaro North and South) required non-impacted
locations close to the earthquake-affected area with similar substrate compositions and
pre-quake taxa. As with other studies based on a Before-After-Control-Impact (BACI)
approach, limitations of such control sites include their inability to provide true replicates
of the treatment effect of interest (e.g., relative sea-level change). There remains some
degree of variability between sites despite best efforts to control for this in the site selection
process [43,44].
3. Results
3.1. Sensitivity Analyses
Tilt assessments showed that landward extension of the analysis windows had little
effect on the uplift values obtained (Figure 4). Regressions of all combinations of analysis
window size showed consistent results, with R
2
values of 0.983, 0.982, and 0.996 for 50 m vs.
200 m, 50 m vs. 500 m, and 200 m vs. 500 m, respectively. One-way ANOVAs showed no
significant difference between the uplift values obtained (F
2,3987
= 0.022, p= 0.978). These
results validated use of the finest-scale assessment window (50
×
50 m) for subsequent
analyses. Sensitivity analyses for the control of horizontal displacement effects showed no
significant difference between the two- and five-degree slope constraints for the
50 ×50 m
analysis windows (one way ANOVA: F
1,2652
= 0.001, p= 0.916). A regression of these results
also showed a high correlation at all uplift values (R
2
= 0.996, see Supplementary Material
Figure S1).
GeoHazards 2021, 2, x FOR PEER REVIEW 10 of 20
significant difference between the two- and five-degree slope constraints for the 50 × 50 m
analysis windows (one way ANOVA: F1,2652 = 0.001, p = 0.916). A regression of these results
also showed a high correlation at all uplift values (R2 = 0.996, see Supplementary Material
Figure S1).
Figure 4. Regressions of uplift values obtained from all combinations of the three analysis window sizes (50 × 50 m, 50 ×
200 m, 50 × 500 m) that differ in their landward dimension perpendicular to the coastline.
3.2. Degree of Uplift
Assessment of the two post-quake time periods showed that the majority of vertical
displacement was co-seismic and associated with the 16 November earthquake event (Fig-
ure 5A,B). Ground level displacements in the period between December 2016 and June
2018 were generally site-specific and lacking in distinct coast-wide trends. Field observa-
tions and aerial photography suggest that the ground-level differences between these Li-
DAR acquisition dates result primarily from erosion and accretion effects of erodable sub-
strates. These include significant discharges of material from adjacent hill-country that
was fuelled by numerous landslides along the coast and nearby mountain ranges. An up-
lift assessment using the most recent (post-quake) LiDAR data enabled the generation of
a complete dataset for all sections of the 100 km study area (Figure 5C). Vertical displace-
ment at the coastline varies from subsidence of nearly 2 m to uplift of over 7 m as meas-
ured within the 50 × 50 m analysis units. Several prominent spatial patterns are evident,
with negligible uplift at Oaro situated at the south end of the study area, an area of very
high uplift near Waipapa Bay and variable degrees of uplift elsewhere (Figure 5C).
3.3. Interaction between Uplift and Substrate Type
Substrate mapping showed that the length of coastline represented by substrate type
was 14.7 km for rocky reef, 26.7 km for boulder fields, 54.3 km for mixed sand-gravel, and
4.4 km for sandy beaches. Evaluation of the interaction between these substrate types and
vertical elevation change using the most recent data showed that the majority of boulder
and rocky reef habitat was uplifted by various degrees in the 04 m range (Figure 6). A
small section of rocky reef that was lifted c. 6 m can also be seen in this plot, which repre-
sents the high uplift area at Waipapa. Uplift also affected the mixed sandgravel and
sandy beach environments to various degrees. Modest degrees of subsidence affected
small sections of coastline within all four of these substrate types, with most of these areas
being located at the far north and south of the study area (as seen in Figure 5).
Figure 4.
Regressions of uplift values obtained from all combinations of the three analysis window sizes (50
×
50 m,
50 ×200 m, 50 ×500 m) that differ in their landward dimension perpendicular to the coastline.
3.2. Degree of Uplift
Assessment of the two post-quake time periods showed that the majority of vertical
displacement was co-seismic and associated with the 16 November earthquake event
(Figure 5A,B)
. Ground level displacements in the period between December 2016 and June
2018 were generally site-specific and lacking in distinct coast-wide trends. Field obser-
vations and aerial photography suggest that the ground-level differences between these
LiDAR acquisition dates result primarily from erosion and accretion effects of erodable
substrates. These include significant discharges of material from adjacent hill-country that
was fuelled by numerous landslides along the coast and nearby mountain ranges. An uplift
assessment using the most recent (post-quake) LiDAR data enabled the generation of a
complete dataset for all sections of the 100 km study area (Figure 5C). Vertical displacement
at the coastline varies from subsidence of nearly 2 m to uplift of over 7 m as measured
within the 50
×
50 m analysis units. Several prominent spatial patterns are evident, with
negligible uplift at Oaro situated at the south end of the study area, an area of very high
uplift near Waipapa Bay and variable degrees of uplift elsewhere (Figure 5C).
GeoHazards 2021,2311
GeoHazards 2021, 2, x FOR PEER REVIEW 11 of 20
(A)
(B)
(C)
Figure 5. Vertical displacement of the Kaikōura coast calculated for two time periods (A) 20122016
and (B) 20122018 using independent differencing analyses and a 5-degree slope constraint to con-
trol for horizontal displacement effects. The LiDAR datasets have comparable resolution but slightly
different coverage. The gap in coverage at c. 35 km on the X axis is the Kaikōura Peninsula. This
area was outside of the LiDAR acquisition extent in the immediate post-quake dataset (December
2016), but was included in the June 2018 acquisition, enabling the analysis of 2012 to 2018 ground-
level changes for the entire study area. (C) Estimated vertical displacement of the entire coastline
between July 2012 and June 2018. Vertical displacements recorded in national geodetic updates to
the Land Information New Zealand (LINZ) survey benchmark network to November 2018 are also
shown for comparison.
Figure 6. Histograms of the degree of uplift experienced within a classification of four substrate
types found on the Kaikōura coast for the period July 2012–June 2018. Calculations used a 50 × 50
m analysis window and a 5-degree slope constraint to control for horizontal displacement effects.
Figure 5.
Vertical displacement of the Kaik
¯
oura coast calculated for two time periods (
A
) 2012–2016
and (
B
) 2012–2018 using independent differencing analyses and a 5-degree slope constraint to control
for horizontal displacement effects. The LiDAR datasets have comparable resolution but slightly
different coverage. The gap in coverage at c. 35 km on the X axis is the Kaik
¯
oura Peninsula. This area
was outside of the LiDAR acquisition extent in the immediate post-quake dataset (December 2016),
but was included in the June 2018 acquisition, enabling the analysis of 2012 to 2018 ground-level
changes for the entire study area. (
C
) Estimated vertical displacement of the entire coastline between
July 2012 and June 2018. Vertical displacements recorded in national geodetic updates to the Land
Information New Zealand (LINZ) survey benchmark network to November 2018 are also shown
for comparison.
3.3. Interaction between Uplift and Substrate Type
Substrate mapping showed that the length of coastline represented by substrate type
was 14.7 km for rocky reef, 26.7 km for boulder fields, 54.3 km for mixed sand-gravel, and
4.4 km for sandy beaches. Evaluation of the interaction between these substrate types and
vertical elevation change using the most recent data showed that the majority of boulder
and rocky reef habitat was uplifted by various degrees in the 0–4 m range (Figure 6). A
small section of rocky reef that was lifted c. 6 m can also be seen in this plot, which
represents the high uplift area at Waipapa. Uplift also affected the mixed sand–gravel
and sandy beach environments to various degrees. Modest degrees of subsidence affected
small sections of coastline within all four of these substrate types, with most of these areas
being located at the far north and south of the study area (as seen in Figure 5).
3.4. Ecological Impacts
Post-earthquake measurements show that algal mortality was severe (>80% loss) in at
least one algal class at nine of the 12 study sites. High mortality (>50%) was absent at only
two sites, both of which were located at Oaro and were the only study sites characterised
by an absence of uplift, thereby functioning as controls. Vertical displacement at the field
survey sites ranged from 0.3 m of subsidence at Oaro South to 5.5 m of uplift at Waipapa
North based on the most recent data (Figure 7).
GeoHazards 2021,2312
GeoHazards 2021, 2, x FOR PEER REVIEW 11 of 20
(A)
(B)
(C)
Figure 5. Vertical displacement of the Kaikōura coast calculated for two time periods (A) 20122016
and (B) 20122018 using independent differencing analyses and a 5-degree slope constraint to con-
trol for horizontal displacement effects. The LiDAR datasets have comparable resolution but slightly
different coverage. The gap in coverage at c. 35 km on the X axis is the Kaikōura Peninsula. This
area was outside of the LiDAR acquisition extent in the immediate post-quake dataset (December
2016), but was included in the June 2018 acquisition, enabling the analysis of 2012 to 2018 ground-
level changes for the entire study area. (C) Estimated vertical displacement of the entire coastline
between July 2012 and June 2018. Vertical displacements recorded in national geodetic updates to
the Land Information New Zealand (LINZ) survey benchmark network to November 2018 are also
shown for comparison.
Figure 6. Histograms of the degree of uplift experienced within a classification of four substrate
types found on the Kaikōura coast for the period July 2012–June 2018. Calculations used a 50 × 50
m analysis window and a 5-degree slope constraint to control for horizontal displacement effects.
Figure 6.
Histograms of the degree of uplift experienced within a classification of four substrate
types found on the Kaik
¯
oura coast for the period July 2012–June 2018. Calculations used a 50
×
50 m
analysis window and a 5-degree slope constraint to control for horizontal displacement effects.
GeoHazards 2021, 2, x FOR PEER REVIEW 12 of 20
3.4. Ecological Impacts
Post-earthquake measurements show that algal mortality was severe (>80% loss) in
at least one algal class at nine of the 12 study sites. High mortality (>50%) was absent at
only two sites, both of which were located at Oaro and were the only study sites charac-
terised by an absence of uplift, thereby functioning as controls. Vertical displacement at
the field survey sites ranged from 0.3 m of subsidence at Oaro South to 5.5 m of uplift at
Waipapa North based on the most recent data (Figure 7).
Figure 7. Summary of earthquake-induced mortality by major intertidal taxa and associated bare
ground changes for 12 sites that experienced various degrees of uplift on the Kaikōura coast. Col-
ours represent the severity of changes in percentage cover from pre-earthquake values as measured
in post-earthquake field surveys within the equivalent intertidal zone with the highest severity rec-
orded over three surveys presented here.
Large brown algae suffered the greatest mortality across all uplifted areas, regardless
of degree of uplift. However, coralline algae also suffered high or severe mortality at all
uplifted sites. These are low-stature base algae that form the primary cover of rocky sub-
strates through much of the mid and low intertidal zones. Fleshy red algae showed highly
variable site-specific contributions to post-quake cover, with some sites experiencing
gains relative to pre-quake levels in the equivalent tidal zone and no obvious relationship
to uplift overall (Figure 7). However, green algae increased at nearly all sites. Ephemeral
species such as the sea lettuce Ulva bloomed extensively in the post-quake mid and low
tidal zones, likely facilitated by the initial loss of competing algal species and the extensive
mortality of intertidal grazers such as limpets and pāua (abalone) at uplifted sites, but also
the extremely warm conditions that prevailed in the 20162017 summer. Bare ground in-
creased at all sites from pre-earthquake values of 120%, consistent with the pattern of
total algal cover change. At some sites including the controls at Oaro but notably at Wai-
papa lagoon, the increase in unvegetated substrate was partly due to sand and gravel
deposition onto rocky shores.
Within the above overall pattern there were many site- and zone-specific nuances in
terms of impacts across the coastline. For example, it was immediately apparent that large
brown algae suffered high mortality at most sites, but these were not necessarily the same
species. For example, the low zone of the highest uplift sites around Waipapa was mostly
dominated by the large southern bull kelp, Durvillaea spp., prior to the earthquake, but
this disappeared completely from these sites post-quake (Figure 8A). Red algal species
comprise much of the diversity of this coastline. These expanded quickly in the low tidal
zone, primarily because they can regenerate from remnant patches and also can repro-
duce, recruit and grow faster than most of the large brown algae that had died. Coralline
algae are tough calcareous species that form an extensive primary cover of rock surfaces.
Figure 7.
Summary of earthquake-induced mortality by major intertidal taxa and associated bare
ground changes for 12 sites that experienced various degrees of uplift on the Kaik
¯
oura coast. Colours
represent the severity of changes in percentage cover from pre-earthquake values as measured in
post-earthquake field surveys within the equivalent intertidal zone with the highest severity recorded
over three surveys presented here.
Large brown algae suffered the greatest mortality across all uplifted areas, regardless
of degree of uplift. However, coralline algae also suffered high or severe mortality at
all uplifted sites. These are low-stature base algae that form the primary cover of rocky
substrates through much of the mid and low intertidal zones. Fleshy red algae showed
highly variable site-specific contributions to post-quake cover, with some sites experiencing
gains relative to pre-quake levels in the equivalent tidal zone and no obvious relationship
to uplift overall (Figure 7). However, green algae increased at nearly all sites. Ephemeral
species such as the sea lettuce Ulva bloomed extensively in the post-quake mid and low
tidal zones, likely facilitated by the initial loss of competing algal species and the extensive
mortality of intertidal grazers such as limpets and p
¯
aua (abalone) at uplifted sites, but
also the extremely warm conditions that prevailed in the 2016–2017 summer. Bare ground
increased at all sites from pre-earthquake values of 1–20%, consistent with the pattern
of total algal cover change. At some sites including the controls at Oaro but notably at
Waipapa lagoon, the increase in unvegetated substrate was partly due to sand and gravel
deposition onto rocky shores.
GeoHazards 2021,2313
Within the above overall pattern there were many site- and zone-specific nuances in
terms of impacts across the coastline. For example, it was immediately apparent that large
brown algae suffered high mortality at most sites, but these were not necessarily the same
species. For example, the low zone of the highest uplift sites around Waipapa was mostly
dominated by the large southern bull kelp, Durvillaea spp., prior to the earthquake, but
this disappeared completely from these sites post-quake (Figure 8A). Red algal species
comprise much of the diversity of this coastline. These expanded quickly in the low
tidal zone, primarily because they can regenerate from remnant patches and also can
reproduce, recruit and grow faster than most of the large brown algae that had died.
Coralline algae are tough calcareous species that form an extensive primary cover of rock
surfaces. As they desiccated and died, the soft sedimentary rocks they were on usually
eroded rapidly and disintegrated [
45
], contributing to gravel deposition and sediment
loads in nearshore waters along the coast (Figure 8B). Some of the worst affected areas
include reefs on Kaik
¯
oura Peninsula such as Wairepo. This one of the longest studied
coastal sites in New Zealand [
39
] and has an extensive intertidal platform. It was covered
in the mid-tidal zone by the bladder alga Hormosira, which suffered severe mortality from
reduced tidal inundation and increased temperatures despite the relatively small degree of
uplift (Figure 8C,D).
GeoHazards 2021, 2, x FOR PEER REVIEW 13 of 20
As they desiccated and died, the soft sedimentary rocks they were on usually eroded rap-
idly and disintegrated [45], contributing to gravel deposition and sediment loads in near-
shore waters along the coast (Figure 8B). Some of the worst affected areas include reefs on
Kaikōura Peninsula such as Wairepo. This one of the longest studied coastal sites in New
Zealand [39] and has an extensive intertidal platform. It was covered in the mid-tidal zone
by the bladder alga Hormosira, which suffered severe mortality from reduced tidal inunda-
tion and increased temperatures despite the relatively small degree of uplift (Figure 8C,D).
Figure 8. Impacts of uplift on the Kaikōura coast. (A) Waipapa Lagoon site on high tide in the post-
quake landscape. Dead and dying bull kelp (Durvillaea spp) and other brown seaweeds can be seen.
The pre-quake high tide mark is at the top of the large rocks, a displacement of nearly 5 m. (B) Reef
erosion at Wairepo six months after the earthquake. The washer was flush with the rock surface
when installed immediately post-quake. (C,D) A graphic illustration of the severity of impacts on
habitat-forming algae at Wairepo. Despite experiencing only modest uplift, nearly all seaweeds in-
cluding Hormosira (in foreground) perished soon after the earthquake.
3.5. Threshold Value for Relative Sea-Change Associated with High Mortality
These results show that uplift values of 0.6 m or higher were consistently associated
with high mortality in habitat-forming brown algae and also coralline algae. Despite wide-
spread increases in green algal cover and some increases in reds, the combined canopy
cover of all algal classes was also reduced by nearly 50% or more at all uplifted sites. This
equates to massive losses in biomass in equivalent tidal zones as a consequence of the
earthquake and reflects both losses in pre-quake populations and the failure of compen-
satory recovery in the post-quake environment. It can be noted that the absence of study
sites in the uplift range 0.1–0.5 m is a limitation for identifying the true ‘threshold’ value
for relative sea-change associated with high mortality on rocky shores. Despite this, the
empirical evidence strongly suggests that these effects occurred with uplift of 0.6 m or
more, and this value is adopted to estimate the extent of high or severe mortality for the
Figure 8.
Impacts of uplift on the Kaik
¯
oura coast. (
A
) Waipapa Lagoon site on high tide in the
post-quake landscape. Dead and dying bull kelp (Durvillaea spp.) and other brown seaweeds can
be seen. The pre-quake high tide mark is at the top of the large rocks, a displacement of nearly
5 m
.
(B) Reef
erosion at Wairepo six months after the earthquake. The washer was flush with the
rock surface when installed immediately post-quake. (
C
,
D
) A graphic illustration of the severity of
impacts on habitat-forming algae at Wairepo. Despite experiencing only modest uplift, nearly all
seaweeds including Hormosira (in foreground) perished soon after the earthquake.
GeoHazards 2021,2314
3.5. Threshold Value for Relative Sea-Change Associated with High Mortality
These results show that uplift values of 0.6 m or higher were consistently associated
with high mortality in habitat-forming brown algae and also coralline algae. Despite
widespread increases in green algal cover and some increases in reds, the combined canopy
cover of all algal classes was also reduced by nearly 50% or more at all uplifted sites.
This equates to massive losses in biomass in equivalent tidal zones as a consequence
of the earthquake and reflects both losses in pre-quake populations and the failure of
compensatory recovery in the post-quake environment. It can be noted that the absence of
study sites in the uplift range 0.1–0.5 m is a limitation for identifying the true ‘threshold’
value for relative sea-change associated with high mortality on rocky shores. Despite this,
the empirical evidence strongly suggests that these effects occurred with uplift of 0.6 m
or more, and this value is adopted to estimate the extent of high or severe mortality for
the whole coast. Although we cannot fully answer the question of a potentially lower
threshold, only a small proportion of the coastline experienced uplift in the 0.1–0.5 m range,
and very little of this area has rocky reef or boulder substrata. Therefore, our estimate of
the extent of impacts would be relatively unaffected by assuming a slightly lower threshold
for relative sea-change.
3.6. Extent of Impacts across 100 km of Coast
Using a threshold value of 0.6 m, we estimate that high or severe mortality of habitat-
forming species has occurred over 87% of the rocky reef and 72% of the boulder habitat
in the study area. The length of coastline involved is 19.4 km for rocky reef and 12.9 km
for boulder habitat. In combination, major impacts have affected over 30 km of coastline
that previously supported highly productive and diverse marine communities in these
intertidal habitats. Note that the coastline considered in these calculations includes the
Oaro control sites and adjacent areas. Nearly all of the remaining coastline exceeded the
0.6 m threshold value for high or severe mortality in habitat-forming brown algae and
coralline algae. Furthermore, there are also rocky coast areas at least 30 km to the north
that are not represented in this study (due to lack of LIDAR surveys), which were similarly
affected [31].
4. Discussion
This study illustrates important considerations and methodological solutions for
producing reliable estimates of relative sea-level change at ecologically relevant scales
across a large study area. Inherent in this are crucial decisions on the selection of data that
best meet these objectives, which typically requires a compromise between the scale and
extent of potentially useful data sources. In this case, the zonation pattern and topography
of the intertidal zone drove the ecological components of interest for which a relatively
fine scale (i.e., tens of metres) is needed to resolve physical environmental changes of
consequence. In contrast, the size of the overall study area is huge in comparison because
of the sheer extent of the natural disaster event. The need, therefore, is for data with high
resolution and large spatial coverage, an ideal that is somewhat of a holy grail.
Along with other options for ground-level change analysis using satellite altimetry
platforms [
46
], airborne LiDAR provides an attractive data acquisition solution because
it can incorporate concurrent high resolution aerial imagery (e.g., 0.2 m resolution in this
case). As exemplified here, this imagery can be very useful for identifying and delineating
the position of mobile landforms such as rivermouths that are problematic for differencing
analyses. While direct field observations are also important to gain an understanding of
these features, the combined approach produces an efficient workflow for these manual
tasks in the analysis. Other aspects of note in this study include the use of largely terrestrial
data to estimate geographical changes in the nearby marine environment. The rationale
for this approach relates to the advantages of LiDAR data in meeting sampling objectives
(large spatial extent and high resolution), which are virtually impossible to reproduce at
this scale using any other method. This exemplifies the challenges of geographical surveys
GeoHazards 2021,2315
of the coastal interface in which the study area is exposed to periodic inundation and where
water depths are too shallow and wave-exposed for use of sonar survey platforms [47].
Our approach also exemplifies the use of sensitivity analyses as a tool for validating
methodological solutions for potentially confounding factors. We applied a nearly flat-
ground slope constraint to the differencing analysis, but we tested more than one slope
threshold to verify its efficacy. The highly correlated results suggest that a slope constraint
of 5 degrees is sufficient for these purposes in a relatively high relief study area, although
this may differ in other analysis contexts due to other combinations of ground sampling
dimensions and sampling window size. Reducing the slope threshold will generally reduce
the number of data points available for the analysis. In our case, however, the 2-degree
slope constraint did not result in the complete loss of data in any of the analysis windows,
and the mean uplift values obtained were very similar (Supplementary Material Figure S1).
Sensitivity analyses were also used to test for tilt effects as a confounding factor in the
direction of interest (perpendicular to the coastline). These analyses provided a very useful
test of assumptions around the transferability of vertical displacement estimates to nearby
locations across the shore profile, thereby addressing the main objective of supporting
intertidal ecological sampling. Within the overall workflow, these tests complement, but
cannot completely replace, the manual inspection of DEMs, differencing results and aerial
imagery to detect geographical irregularities that influence the interpretation of results
at key locations. This is exemplified by the block faulting effects on the Papatea Fault
that are visible in all three of the above data sources, but could be easily missed without
the benefit of field observations (Figure 8). In this case they directly affected our area
of interest in the new intertidal zone configuration and required manually constrained
sampling domains for the estimation of vertical displacement at those locations
(Figure 2)
.
Overall, these aspects show that the combined methodological approach of (a) using
adjacent ‘terrestrial’ data to estimate large-scale change in the nearby intertidal zone,
and (b) sensitivity analyses for confounding factors provides a computationally efficient
approach for the estimation of vertical displacement and associated relative sea-level
changes in a difficult sampling environment.
4.1. Contribution of Temporal Changes
Along with the above approaches for estimating co-seismic displacement effects on rel-
ative sea levels at intertidal locations, the potential for ongoing change must be addressed
and considered. To provide an initial indication of potential changes at the whole-coast
scale, we used the available LiDAR data to test for further post-seismic vertical displace-
ment to 18 months post-earthquake, which is also an important time period in the context
of disaster recovery. The decomposition of ground-level changes between the co-seismic
and post-seismic periods showed that the majority of vertical displacement was associated
with the 16 November earthquake event. This is consistent with other studies that have
shown post-seismic afterslip effects associated with the Kaik
¯
oura earthquake
[41,42]
, for
which the main locations exhibiting vertical motion are located farther north (i.e., outside
of our study area). Although there has been some degree of horizontal afterslip within our
study area, these effects are largely obscured by the use of slope constraints in our analysis.
Importantly, however, our results for the post-seismic period show there have been con-
siderable gains and losses in ground elevation at numerous sites along the coastline, even
though highly mobile landforms such as rivermouths and earthquake-damaged areas such
as road corridors were removed from the analysis. These effects indicate the contribution
of important ongoing topographical changes that involve both accretion and erosion. Both
processes continue to affect the new intertidal zone in a highly variable manner.
Field observations showed that these dynamics included extensive gravel depositions
that covered areas of former reef and boulder fields at several locations. Additionally,
many of these rocky areas are experiencing significant erosion from accelerated weathering
in their uplifted positions, which is particularly prominent on mudstone platforms. At
these sites, changes to the wetting and the additional drying time caused by uplift has
GeoHazards 2021,2316
exacerbated tension cracking, essentially shattering the upper few centimetres of the
substrate surface. This shattered material is then quickly eroded away by wind and
wave action, and is repeated in successful cycles. These reefs typically erode at 1–2 mm
annually [
45
,
48
], but lost up to 30 mm within 6 months post-earthquake [
31
]. At many
sites, these accelerated erosion effects have been ongoing since the initial uplift event,
suggesting that they may continue until new wave-cut platforms have lowered sufficiently
to provide wetting times that promote substrate stabilisation, consistent with established
theory [
49
,
50
]. By extension, these same conditions may be required to support the eventual
recovery of characteristic algal species at densities comparable to their former abundance
because many of the rocky surfaces are too unstable for effective recruitment of large algae.
Both of the above phenomena have obvious relevance for the re-establishment of biogenic
algal cover and are significant additional stressors.
4.2. Impact Thresholds and Contributing Factors
Our analyses indicate that the threshold of major impacts is in the vicinity of a quar-
ter of the tidal range (approximately 2 m) for the characteristic habitat-forming algal
communities in this area. The four least-uplifted of our sampling sites outside of Oaro
(which function as ‘control’ sites) provide a direct test of relative sea-level changes in the
0.6 m–0.9 m
range. Changes in tidal cover at these sites were evidently beyond the adap-
tive threshold of the algal communities they previously supported, causing widespread
mortality in the intertidal zone (Figure 8C,D). This interpretation is consistent with the
general zonational pattern of these habitat-forming species. However, the empirical data
also show that compensatory recovery has not occurred in the equivalent post-quake tidal
zone and it is the combination of the two processes that are responsible for the net impact
as assessed in this study. This finding is consistent with our central hypothesis in which a
lag effect would occur in consideration of likely recruitment rates and that would manifest
as net losses in the short term. However, the severity of these losses was even greater than
expected. This primarily relates to conditions in the new post-quake intertidal area, in
which only sparse habitat-forming algae were recorded and despite the fact that many
individual algae were also uplifted into that zone from populations that were previously
subtidal. This highlights the fragility of the post-quake environment and indicates the
need for further research on the nature of contributing factors and potential timelines for
appreciable recovery to occur.
Once populations of large algae are removed, recovery can be slow where reproduc-
tive adults become widely separated due to connectivity effects between suitable habitat
for re-colonisation and the remaining recruitment sources [
32
]. A wide range of processes
are likely hindering recovery in the post-earthquake landscape, including the now widely
dispersed adult populations, the relatively short distance of propagule dispersal (usu-
ally only tens of meters), and limited ability of drifting detached reproductive algae to
reach sites [
37
]. This emphasises the importance of the remaining remnant populations
of reproductive adults. Our observations indicate that many of these individuals may
have experienced, and may continue to be experiencing, heightened vulnerability due to
interactions between relative sea-level changes and other processes. In particular, there
is mounting evidence to suggest that previously stable subtidal substrates have become
unstable and are now weathering faster as a consequence of vertical displacement into
areas of higher wave energy. This hypothesis might explain the initial loss of algae affixed
to such substrates that would otherwise appear to have remained with a suitable tidal zone
for the species, and the same effects may be hindering the re-establishment of new recruits
in these areas.
4.3. Stressors and Recovery Prospects
Related post-earthquake studies on the large southern bull kelp, Durvillaea spp., which
occupies the intertidal–subtidal fringe on wave-exposed shores, show that it is particularly
susceptible to desiccation with prolonged exposure, especially when wave splash is low and
GeoHazards 2021,2317
temperatures are high during low tide [
51
]. Other large brown algae such as Carpophyllum
maschalocarpum and Cystophora spp. also occur in the lowest margins of the intertidal zone
and typically die back to the lowest portion of the tidal zone if tides are exceptionally low,
wave splash is small, and air temperatures are high. Losses were also observed in the
formerly extensive mid-intertidal beds of the fucoid Hormosira. This is the most desiccation-
tolerant of the fucoid species (the large brown algae of the intertidal zone) and typically
recovers quickly [
52
], even after prolonged exposure at low tides. For example, the
0.9 m
of
uplift experienced by the Wairepo reef platform resulted in wetting times of 2–2.5 h of the
5 h of pre-earthquake daily high tide inundation in the semi-diurnal tidal cycle. Despite
remaining within the tidal zone, desiccation stress from air temperatures often exceeding
40
C above the reef surface and elevated water temperatures as tides covered the reefs
to only shallow depths, proved too harsh for Hormosira to persist. In most places it died
off over a period of 6 weeks post-earthquake. This species facilitates productivity and
very high diversity by shading other species below its canopy, and its near-total loss was
catastrophic for local diversity.
Interactions between the degree of uplift and topography of the shore platform are
highlighted in the above processes and provide a further layer of complexity that underpins
the pattern of loss. As the Hormosira example shows, relatively small changes in intertidal
position can affect water temperatures and susceptibility to desiccation that may represent
a tipping point leading to complete loss of the pre-existing population. Furthermore, these
losses can involve extensive areas where the intertidal topography is relatively flat, as is
a feature of many reef platforms on the Kaik
¯
oura coast. These topographical aspects are
additional to the coastal erosion and deposition effects discussed above, which can also
be catastrophic for both remnant algae of uplifted surfaces and newly established recruits.
Fine silts are also abundant in the post-earthquake environment and add further stresses
associated with the smothering of rocky substrates and occlusion of nearshore waters,
leading to reduced light transmission and impacts on photosynthesis.
5. Conclusions
This work has been an important milestone in relating ecological damage along an
extensive stretch of coastline to vertical displacement caused by one of the major seismic
events in modern times. This is the first study to quantify relative sea-level changes at the
position of the new intertidal environment and the first to estimate the extent of earthquake
impacts on major habitat-forming algal species that are characteristic of the Kaik
¯
oura region.
In doing so, we demonstrated a practical workflow for translating high-resolution data
from nearby terrestrial areas to adjacent data-poor intertidal areas that includes sensitivity
analyses to assess validity.
Our assessment of major impacts associated with the relative sea-level change reflects
losses of habitat-forming macroalgae in the equivalent pre-quake and post-quake intertidal
zones compounded by a lack of recruitment into the latter. Our whole-coast estimate
of c. 90% mortality of large algae on a percentage cover basis provides some indication
of the tenuous starting point upon which future recovery depends. The intensity and
frequency of hydro-ecological changes and continuing interactions between stressors are
key influences on recovery processes that will have legacy effects for many years to come in
this coastal area, and similarly in other natural disaster contexts. Against this broad-scale
backdrop it will be important to follow the fate of the remnant populations in addition
to the establishment of new recruits. Both remain vulnerable to the effects of additional
stressors, including those already observable and potentially for additional extreme events,
particularly heat waves, in future years.
Supplementary Materials:
The following are available online at https://www.mdpi.com/article/
10.3390/geohazards2040016/s1, Figure S1: Regressions of uplift values for 2-degree and 5-degree
slope constraints for the three analysis window sizes that differed in their landward dimension
perpendicular to the coastline. Figure S2: Vertical displacement of the Kaik
¯
oura coast for the period
July 2012–June 2018 within three analysis window sizes (50
×
50 m, 50
×
200 m, 50
×
500 m) differing
GeoHazards 2021,2318
in their landward dimension. These calculations used a 5-degree slope constraint to control for
horizontal displacement effects. Figure S3: Density plot of the degree of uplift experienced within
a classification of four substrate types found on the Kaik
¯
oura coast for the period July 2012–June
2018. Calculations used a 50
×
50 m analysis window and a 5-degree slope constraint to control for
horizontal displacement effects. Table S1: Post-earthquake algal cover expressed as the percentage of
pre-earthquake values for 12 sites on the Kaik
¯
oura coast. Data show the minimum values recorded
over three post-quake sampling campaigns during the period to 18-months post-quake in which
algal mortality was occurring at variable rates. The average percentage cover of four algal classes
(brown, red, corallines, green) was recorded (species by species and then grouped) in 1 m
2
quadrats
sampled at random positions throughout the algal-dominated mid- and low intertidal zones. The
total cover value can sum to > 100% due to layering and overlapping of algal species.
Author Contributions:
Conceptualization, S.O., D.R.S.; methodology, S.O., D.R.S.; formal analysis,
S.O., H.S.F., D.R.S.; investigation, S.O., T.A., S.G., R.D.; resources, D.R.S.; data curation, S.O., H.S.F.;
writing—original draft preparation, S.O.; writing—review and editing, S.O., D.R.S.; visualization,
S.O., H.S.F.; funding acquisition, S.O., D.R.S. All authors have read and agreed to the published
version of the manuscript.
Funding:
This research was funded by the Ministry of Business Innovation and Employment (MBIE)
Endeavour Fund (UOCX1704), with additional support from the Ministry for Primary Industries
(MPI) (KAI2016-05) and the Sustainable Seas National Science Challenge (UOA20203).
Institutional Review Board Statement: Ethical review was not required for this study.
Informed Consent Statement: Not applicable.
Data Availability Statement:
Data are contained within the article or supplementary material.
LiDAR datasets are available from Land Information New Zealand or the commissioning agency
(Table 1).
Acknowledgments:
We thank our funders, and staff at the University of Canterbury, particularly
Ian Wright and Sharyn Goldstein, and others at the National Institute of Water and Atmospheric
Research (NIWA) for assisting with initial post-disaster survey work and gaining access to sites.
Thanks to Stephanie Mangan, Thomas Falconer, Dave Taylor and Paul South for assisting with field
surveys or data preparation, and John Pirker for iwi liaison in support of this work.
Conflicts of Interest:
The authors declare no conflict of interest. The sponsors had no role in the
design, execution, interpretation, or writing of the study.
References
1.
Cahoon, D.R. Estimating relative sea-level rise and submergence potential at a coastal wetland. Estuaries Coasts
2015
,38, 1077–1084.
[CrossRef]
2.
Orchard, S.; Hughey, K.F.D.; Measures, R.; Schiel, D.R. Coastal tectonics and habitat squeeze: Response of a tidal lagoon to
co-seismic sea-level change. Nat. Hazards 2020,103, 3609–3631. [CrossRef]
3.
Shugar, D.H.; Walker, I.J.; Lian, O.B.; Eamer, J.B.R.; Neudorf, C.; McLaren, D.; Fedje, D. Post-glacial sea-level change along the
Pacific coast of North America. Quat. Sci. Rev. 2014,97, 170–192. [CrossRef]
4.
Stammer, D.; Cazenave, A.; Ponte, R.M.; Tamisiea, M.E. Causes for contemporary regional sea level changes. Annu. Rev. Mar. Sci.
2013,5, 21–46. [CrossRef] [PubMed]
5.
Cahoon, D.R.; Reed, D.J.; Day, J.W. Estimating shallow subsidence in microtidal salt marshes of the southeastern United States:
Kaye and Barghoorn revisited. Mar. Geol. 1995,128, 1–9. [CrossRef]
6.
Rybczyk, J.M.; Cahoon, D.R. Estimating the potential for submergence for two wetlands in the Mississippi River Delta. Estuaries
2002,25, 985–998. [CrossRef]
7.
Woodroffe, C.D.; Rogers, K.; McKee, K.L.; Lovelock, C.E.; Mendelssohn, I.A.; Saintilan, N. Mangrove sedimentation and response
to relative sea-level rise. Annu. Rev. Mar. Sci. 2016,8, 243–266. [CrossRef]
8.
Berkes, F.; Colding, J.; Folke, C. Navigating Social-Ecological Systems: Building Resilience for Complexity and Change; Cambridge
University Press: Cambridge, UK; New York, NY, USA, 2003.
9. Holling, C.S. Resilience and stability of ecological systems. Annu. Rev. Ecol. Syst. 1973,4, 1–23. [CrossRef]
10.
Martinez, M.L.; Taramelli, A.; Silva, R. Resistance and resilience: Facing the multidimensional challenges in coastal areas. J. Coast.
Res. 2017,77, 1–6. [CrossRef]
11. Bilek, S.L.; Lay, T. Subduction zone megathrust earthquakes. Geosphere 2018,14, 1468–1500. [CrossRef]
12.
Orchard, S.; Schiel, D.R. Enabling nature-based solutions to climate change on a peri-urban sandspit in Christchurch, New
Zealand. Reg. Environ. Chang. 2021,21, 66. [CrossRef]
GeoHazards 2021,2319
13.
Saunders, M.I.; Albert, S.; Roelfsema, C.M.; Leon, J.X.; Woodroffe, C.D.; Phinn, S.R.; Mumby, P.J. Tectonic subsidence provides
insight into possible coral reef futures under rapid sea-level rise. Coral Reefs 2016,35, 155–167. [CrossRef]
14.
Church, J.A.; Clark, P.U.; Cazenave, A.; Gregory, J.M.; Jevrejeva, S.; Levermann, A.; Merrifield, M.A.; Milne, G.A.; Nerem, R.S.;
Nunn, P.D.; et al. Sea level change. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group to the Fifth
Assessment Report of the Intergovernmental Panel on Climate Change; Stocker, T.F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S.K.,
Boschung, J., Nauels, A., Xia, Y., Bex, V., Midgley, P.M., Eds.; Cambridge University Press: Cambridge, UK; New York, NY,
USA, 2013.
15. Nicholls, R.J.; Cazenave, A. Sea-level rise and its impact on coastal zones. Science 2010,328, 1517–1520. [CrossRef]
16.
Simms, A.R.; Anderson, J.B.; DeWitt, R.; Lambeck, K.; Purcell, A. Quantifying rates of coastal subsidence since the last interglacial
and the role of sediment loading. Glob. Planet. Chang. 2013,111, 296–308. [CrossRef]
17.
Albert, S.; Saunders, M.I.; Roelfsema, C.M.; Leon, J.X.; Johnstone, E.; Mackenzie, J.R.; Hoegh-Guldberg, O.; Grinham, A.R.; Phinn,
S.R.; Duke, N.C.; et al. Winners and losers as mangrove, coral and seagrass ecosystems respond to sea-level rise in Solomon
Islands. Environ. Res. Lett. 2017,12, 94009. [CrossRef]
18.
Quigley, M.C.; Hughes, M.W.; Bradley, B.A.; van Ballegooy, S.; Reid, C.; Morgenroth, J.; Horton, T.; Duffy, B.; Pettinga, J.R.
The 2010–2011 Canterbury Earthquake Sequence: Environmental effects, seismic triggering thresholds and geologic legacy.
Tectonophysics 2016,672–673, 228–274. [CrossRef]
19.
Hughes, M.W.; Quigley, M.C.; van Ballegooy, S.; Deam, B.L.; Bradley, B.A.; Hart, D.E.; Measures, R. The sinking city: Earthquakes
increase flood hazard in Christchurch, New Zealand. GSA Today 2015,25, 4–10. [CrossRef]
20.
Orchard, S. Floodplain Restoration principles for the Avon-
¯
Ot
¯
akaro Red Zone: Case Studies and Recommendations; Avon
¯
Ot
¯
akaro Network
(Publisher): Christchurch, New Zealand, 2017; p. 40.
21.
Potter, S.H.; Becker, J.S.; Johnston, D.M.; Rossiter, K.P. An overview of the impacts of the 2010–2011 Canterbury earthquakes. Int.
J. Disaster Risk Reduct. 2015,14, 6–14. [CrossRef]
22.
Orchard, S.; Hughey, K.F.D.; Schiel, D.R. Risk factors for the conservation of saltmarsh vegetation and blue carbon revealed by
earthquake-induced sea-level rise. Sci. Total Environ. 2020,746, 141241. [CrossRef]
23.
Orchard, S.; Hickford, M.J.H. Protected Area Effectiveness for Fish Spawning Habitat in Relation to Earthquake-Induced
Landscape Change. In Sustainable Bioresource Management: Climate Change Mitigation and Natural Resource Conservation; Maiti,
R., Rodríguez, H.G., Kumari, C.A., Mandal, D., Sarkar, N.C., Eds.; Apple Academic Press: Waretown, NJ, USA, 2020; p. 526.
Available online: https://www.routledge.com/Sustainable-Bioresource-Management-Climate-Change-Mitigation-and-Natural/
Maiti-Gonzalez-Rodriguez-Kumari-Mandal/p/book/9780429284229 (accessed on 1 September 2021).
24.
Orchard, S.; Hickford, M.J.H.; Schiel, D.R. Earthquake-induced habitat migration in a riparian spawning fish has implications for
conservation management. Aquat. Conserv. Mar. Freshwat. Ecosyst. 2018,28, 702–712. [CrossRef]
25.
Jaramillo, E.; Dugan, J.E.; Hubbard, D.M.; Melnick, D.; Manzano, M.; Duarte, C.; Campos, C.; Sanchez, R. Ecological implications
of extreme events: Footprints of the 2010 earthquake along the Chilean coast. PLoS ONE 2012,7, e35348. [CrossRef]
26.
Rodil, I.F.; Jaramillo, E.; Hubbard, D.M.; Dugan, J.E.; Melnick, D.; Velasquez, C. Responses of dune plant communities to
continental uplift from a major earthquake: Sudden releases from coastal squeeze. PLoS ONE 2015,10, e0124334. [CrossRef]
27.
Holden, C.; Kaneko, Y.; D’Anastasio, E.; Benites, R.; Fry, B.; Hamling, I.J. The 2016 Kaik
¯
oura Earthquake revealed by kinematic
source inversion and seismic wavefield simulations: Slow rupture propagation on a geometrically complex crustal fault network.
Geophys. Res. Lett. 2017,44, 11320–11328. [CrossRef]
28.
Xu, W.; Feng, G.; Meng, L.; Zhang, A.; Ampuero, J.P.; Bürgmann, R.; Fang, L. Transpressional rupture cascade of the 2016 Mw 7.8
Kaikoura Earthquake, New Zealand. J. Geophys. Res. Solid Earth 2018,123, 2396–2409. [CrossRef]
29.
Hamling, I.J.; Hreinsdóttir, S.; Clark, K.; Elliott, J.; Liang, C.; Fielding, E.; Litchfield, N.; Villamor, P.; Wallace, L.; Wright, T.J.; et al.
Complex multifault rupture during the 2016 Mw 7.8 Kaikoura earthquake, New Zealand. Science
2017
,356, eaam719. [CrossRef]
[PubMed]
30.
Clark, K.J.; Nissen, E.K.; Howarth, J.D.; Hamling, I.J.; Mountjoy, J.J.; Ries, W.F.; Jones, K.; Goldstien, S.; Cochran, U.A.; Villamor,
P.; et al. Highly variable coastal deformation in the 2016 MW7.8 Kaik
¯
oura earthquake reflects rupture complexity along a
transpressional plate boundary. Earth Planet. Sci. Lett. 2017,474, 334–344. [CrossRef]
31.
Alestra, T.; Gerrity, S.; Dunmore, R.A.; Crossett, D.; Orchard, S.; Schiel, D.R. Rocky Reef Impacts of the 2016 Kaik
¯
oura Earthquake:
Extended Monitoring of Nearshore Habitats and Communities to 3.5 Years. New Zealand Aquatic Environment and Biodiversity Report No.
253; Ministry for Primary Industries: Wellington, New Zealand, 2021; p. 46.
32.
Schiel, D.R.; Alestra, T.; Gerrity, S.; Orchard, S.; Dunmore, R.; Pirker, J.; Lilley, S.; Tait, L.; Hickford, M.; Thomsen, M. The Kaik
¯
oura
earthquake in southern New Zealand: Loss of connectivity of marine communities and the necessity of a cross-ecosystem
perspective. Aquat. Conserv. Mar. Freshwat. Ecosyst. 2019,29, 1520–1534. [CrossRef]
33.
Tait, L.W.; Orchard, S.; Schiel, D.R. Missing the forest and the trees: Utility, limits and caveats for drone imaging of coastal marine
ecosystems. Remote. Sens. 2021,13, 3136. [CrossRef]
34.
Gerrity, S.; Alestra, T.; Fischman, H.S.; Schiel, D.R. Earthquake effects on abalone habitats and populations in southern New
Zealand. Mar. Ecol. Prog. Ser. 2020,656, 153–161. [CrossRef]
35.
Orchard, S.; Falconer, T.; Fischman, H.; Schiel, D.R. Beach Dynamics and Recreational Access Changes on an Earthquake-Uplifted Coast;
Marlborough District Council: Blenheim, New Zealand, 2020; p. 42. Available online: https://hdl.handle.net/10092/101043
(accessed on 1 September 2021).
GeoHazards 2021,2320
36.
Schiel, D.R. Biogeographic patterns and long-term changes on New Zealand coastal reefs: Non-trophic cascades from diffuse and
local impacts. J. Exp. Mar. Biol. Ecol. 2011,400, 33–51. [CrossRef]
37.
Hawes, N.A.; Taylor, D.I.; Schiel, D.R. Transport of drifting fucoid algae: Nearshore transport and potential for long distance
dispersal. J. Exp. Mar. Biol. Ecol. 2017,490, 34–41. [CrossRef]
38.
Schiel, D.R.; Foster, M.S. The population biology of large brown seaweeds: Ecological consequences of multiphase life histories in
dynamic coastal environments. Annu. Rev. Ecol. Evol. Syst. 2006,37, 343–372. [CrossRef]
39.
Lilley, S.A.; Schiel, D.R. Community effects following the deletion of a habitat-forming alga from rocky marine shores. Oecologia
2006,148, 672–681. [CrossRef] [PubMed]
40.
Hamling, I.J.; D’Anastasio, E.; Wallace, L.M.; Ellis, S.; Motagh, M.; Samsonov, S.; Palmer, N.; Hreinsdóttir, S. Crustal deformation
and stress transfer during a propagating earthquake sequence: The 2013 Cook Strait sequence, central New Zealand. J. Geophys.
Res. Solid Earth 2014,119, 6080–6092. [CrossRef]
41.
Jiang, Z.; Huang, D.; Yuan, L.; Hassan, A.; Zhang, L.; Yang, Z. Coseismic and postseismic deformation associated with the 2016
Mw 7.8 Kaikoura earthquake, New Zealand: Fault movement investigation and seismic hazard analysis. Earth Planets Space
2018
,
70, 1–14. [CrossRef]
42.
Wallace, L.M.; Hreinsdóttir, S.; Ellis, S.; Hamling, I.; D’Anastasio, E.; Denys, P. Triggered slow slip and afterslip on the Southern
Hikurangi Subduction Zone following the Kaik¯
oura Earthquake. Geophys. Res. Lett. 2018,45, 4710–4718. [CrossRef]
43.
Stewart-Oaten, A.; Murdoch, W.W.; Parker, K.R. Environmental Impact Assessment: “Pseudoreplication” in Time? Ecology
1986
,
67, 929–940. [CrossRef]
44.
Underwood, A.J. Beyond BACI: The detection of environmental impacts on populations in the real, but variable, world. J. Exp.
Mar. Biol. Ecol. 1992,161, 145–178. [CrossRef]
45.
Stephenson, W.J.; Kirk, R.M. Rates and patterns of erosion on inter-tidal shore platforms, Kaikoura Peninsula, South Island, New
Zealand. Earth Surf. Process. Landf. 1998,23, 1071–1085. [CrossRef]
46. Fu, L.-L.; Cazenave, A. Satellite Altimetry and Earth Sciences; Academic Press: Cambridge, MA, USA, 2001; p. 463.
47. Mayer, L.A. Frontiers in seafloor mapping and visualization. Mar. Geophys. Res. 2006,27, 7–17. [CrossRef]
48. Stephenson, W.J.; Kirk, R.M.; Hemmingsen, M.A. Forty three years of micro-erosion meter monitoring of erosion rates on shore
platforms at Kaik¯
oura Peninsula, South Island, New Zealand. Geomorphology 2019,344, 1–9. [CrossRef]
49. Edwards, A.B. Wave action in shore platform formation. Geol. Mag. 2009,88, 41–49. [CrossRef]
50.
Stephenson, W.J.; Kirk, R.M. Development of shore platforms on Kaikoura Peninsula, South Island, New Zealand: II: The role of
subaerial weathering. Geomorphology 2000,32, 43–56. [CrossRef]
51.
Thomsen, M.S.; Mondardini, L.; Thoral, F.; Gerber, D.; Montie, S.; South, P.M.; Schiel, D.R. Cascading impacts of earthquakes and
extreme heatwaves have destroyed populations of an iconic marine foundation species. Divers. Distrib. 2021,00, 1–15.
52.
Brown, M.T. Effects of desiccation on photosynthesis of intertidal algae from a southern New Zealand shore. Bot. Mar.
1987
,
30, 121–128. [CrossRef]
... In the case of intertidal marine systems, much of the biophysical infrastructure on which species and communities build is affected by a wide range of stressors operating over many spatial and temporal scales. The litany of stressors is long and includes eutrophication, marine heat waves, overfishing, invasive species, storms and wave events, coastal development, and sediment from intensive land use, among others (e.g., Schiel, 2009), and additional step-change events (e.g., Orchard et al., 2021). Each of these is known to affect coastal ecosystems through impacts on vulnerable species, ecological structure, and diversity, thereby altering ecological functions and services. ...
... Although originating inland, the stress release activated a large number of faults in a northeasterly direction affecting extensive areas of land and sea Hamling et al., 2017;Gusman et al., 2018). Vertical displacement affected over 130 km of coastline in a highly variable manner but predominantly in the direction of uplift Orchard et al., 2021). Impacts on anthropogenic infrastructure included severe damage to road and rail networks that run close to the sea in this area (Kaiser et al., 2017). ...
... Major changes to relative sea-levels, associated with displacement, caused long-lasting effects in comparison to the tidal range of c.2 m. Broad-scale land and seascape changes included the generation of over 170 ha of new terrestrial land and extensive remodeling of intertidal ecosystems (Orchard et al., 2021). Environmental impacts included widespread mortality of algae, invertebrates and fish along virtually the entire coastline, which effectively reset the nearshore ecosystem . ...
Article
Full-text available
Understanding the resilience and recovery processes of coastal marine ecosystems is of increasing importance in the face of increasing disturbances and stressors. Large-scale, catastrophic events can re-set the structure and functioning of ecosystems, and potentially lead to different stable states. Such an event occurred in south-eastern New Zealand when a Mw 7.8 earthquake lifted the coastline by up to 6 m. This caused widespread mortality of intertidal algal and invertebrate communities over 130 km of coast. This study involved structured and detailed sampling of three intertidal zones at 16 sites nested into four degree of uplift (none, 0.4–1, 1.5–2.5, and 4.5–6 m). Recovery of large brown algal assemblages, the canopy species of which were almost entirely fucoids, were devastated by the uplift, and recovery after 4 years was generally poor except at sites with < 1 m of uplift. The physical infrastructural changes to reefs were severe, with intertidal emersion temperatures frequently above 35°C and up to 50°C, which was lethal to remnant populations and recruiting algae. Erosion of the reefs composed of soft sedimentary rocks was severe. Shifting sand and gravel covered some lower reef areas during storms, and the nearshore light environment was frequently below compensation points for algal production, especially for the largest fucoid Durvillaea antarctica/poha. Low uplift sites recovered much of their pre-earthquake assemblages, but only in the low tidal zone. The mid and high tidal zones of all uplifted sites remained depauperate. Fucoids recruited well in the low zone of low uplift sites but then were affected by a severe heat wave a year after the earthquake that reduced their cover. This was followed by a great increase in fleshy red algae, which then precluded recruitment of large brown algae. The interactions of species’ life histories and the altered physical and ecological infrastructure on which they rely are instructive for attempts to lessen manageable stressors in coastal environments and help future-proof against the effects of compounded impacts.
Article
On tectonically active coasts, there is a dearth of erosion data documenting how rock coasts adjust (either fast or slow) in response to marine and subaerial processes immediately after coseismic uplift. Here we report erosion rates and evidence of reshaping of shore platform morphology at Kaikōura Peninsula, South Island, New Zealand, following the November 2016 Kaikōura 7.8 (Mw) earthquake, that uplifted platforms by ~1 m and extended their widths. High-resolution topographic data obtained from quarterly surveys over four years using a micro-erosion meter (MEM) and Structure-from-Motion Multi-View Stereo (SfM-MVS) surveys have provided rates of erosion and visual representation of surface morphologies. MEM data revealed variations in erosion, weathering and deposition rates across lithology, tidal positions, and platform elevation after the uplift. After four years, surface downwearing rates for all platforms were on average 2.25 mm/yr, a 104% increase from the pre-uplift rate of 1.10 mm/yr. Average lowering rates on limestone, hard, and soft mudstone platforms were 1.19 mm/yr, 2.31 mm/yr, and 3.21 mm/yr, respectively. Results show a change in patterns of erosion rates and faster rates on mudstone than limestone lithologies, but both faster when compared to pre-uplift rates. Previously reported seasonal trends in erosion rates have disappeared because post-uplift erosion rates are similar during the summer and winter. In contrast, statistically significant differences in lowering rates now exist across rock lithology and elevation. On one MEM site on the harder mudstone platform, a large increase from a pre-uplift erosion rate of 0.43 mm/yr to 19.23 mm/yr (1-year after uplift) and subsequent decline to 1.54 mm/yr after four years demonstrates the role of block detachment not previously seen in the MEM data from Kaikōura. For the first time, we complement MEM data with SfM-MVS-derived orthomosaics to provide evidence of changing rock morphology and processes such as granular disintegration, flaking and algal growth. Results from this study demonstrate how tectonism can fundamentally alter the way in which rock shore erosion rates are influenced by waves, tides, and weathering processes.
Article
After New Zealand's 7.8 Mw Kaikōura earthquake in late 2016 an unexpected anthropogenic effect involved increased motorised vehicle access to beaches. We show how these effects were generated by landscape reconfiguration associated with coastal uplift and widening of high-tide beaches, and present analyses of the distribution of natural environment values in relation to vehicle movements and impacts. Access changes led to extensive vehicle tracking in remote areas that had previously been protected by natural barriers. New dunes formed seaward of old dunes and have statutory protection as threatened ecosystems, yet are affected by vehicle traffic. Nesting grounds of nationally vulnerable banded dotterel (Charadrius bicinctus bicinctus) co-occur with vehicle tracking. An artificial nest experiment showed that vehicle strikes pose risks to nesting success, with 91% and 83% of nests destroyed in high and moderate-traffic areas, respectively, despite an increase in suitable habitat. Despite gains for recreational vehicle users there are serious trade-offs with environmental values subject to legal protection and associated responsibilities for management authorities. In theory, a combination of low-impact vehicle access and environmental protection could generate win-win outcomes from the landscape changes, but is difficult to achieve in practice. Detailed information on sensitive areas would be required to inform designated vehicle routes as a potential solution, and such sensitivities are widespread. Alternatively, vehicle access areas that accommodate longstanding activities such as boat launching could be formally established using identified boundaries to control impacts further afield. Difficulties for the enforcement of regulatory measures in remote areas also suggest a need for motivational strategies that incentivise low-impact behaviours. We discuss options for user groups to voluntarily reduce their impacts, the importance of interactions at the recreation-conservation nexus, and need for timely impact assessments across the social-ecological spectrum after physical environment changes -- all highly transferable principles for other natural hazard and disaster recovery settings worldwide.
Preprint
Full-text available
After New Zealand's 7.8 Mw Kaikōura earthquake in late 2016 an unexpected anthropogenic effect involved increased motorised vehicle access to beaches. We show how these effects were generated by landscape reconfiguration associated with coastal uplift and widening of high-tide beaches, and present analyses of the distribution of natural environment values in relation to vehicle movements and impacts. Access changes led to extensive vehicle tracking in remote areas that had previously been protected by natural barriers. New dunes formed seaward of old dunes and have statutory protection as threatened ecosystems, yet are affected by vehicle traffic. Nesting grounds of nationally vulnerable banded dotterel ( Charadrius bicinctus bicinctus ) co-occur with vehicle tracking. An artificial nest experiment showed that vehicle strikes pose risks to nesting success, with 91% and 83% of nests destroyed in high and moderate-traffic areas, respectively, despite an increase in suitable habitat. Despite gains for recreational vehicle users there are serious trade-offs with environmental values subject to legal protection and associated responsibilities for management authorities. In theory, a combination of low-impact vehicle access and environmental protection could generate win-win outcomes from the landscape changes, but is difficult to achieve in practice. Detailed information on sensitive areas would be required to inform designated vehicle routes as a potential solution, and such sensitivities are widespread. Alternatively, vehicle access areas that accommodate longstanding activities such as boat launching could be formally established using identified boundaries to control impacts further afield. Difficulties for the enforcement of regulatory measures in remote areas also suggest a need for motivational strategies that incentivise low-impact behaviours. We discuss options for user groups to voluntarily reduce their impacts, the importance of interactions at the recreation-conservation nexus, and need for timely impact assessments across the social-ecological spectrum after physical environment changes -- all highly transferable principles for other natural hazard and disaster recovery settings worldwide.
Technical Report
Full-text available
This report contributes to a collaborative project between the Marlborough District Council (MDC) and University of Canterbury (UC) which aims to help protect and promote the recovery of native dune systems on the Marlborough coast. It is centred around the mapping of dune vegetation and identification of dune protection zones for old-growth seed sources of the native sand-binders spinifex (Spinifex sericeus) and pīngao (Ficinia spiralis). Both are key habitat-formers associated with nationally threatened dune ecosystems, and pīngao is an important weaving resource and Ngāi Tahu taonga species. The primary goal is to protect existing seed sources that are vital for natural regeneration following major disturbances such as the earthquake event. Several additional protection zones are also identified for areas where new dunes are successfully regenerating, including areas being actively restored in the Beach Aid project that is assisting new native dunes to become established where there is available space.
Article
Full-text available
Aim Ecologists traditionally study how contemporary local processes, such as biological interactions and physical stressors, affect the distribution and abundance of organisms. By comparison, biogeographers study the distribution of the same organisms, but focus on historic, larger-scale processes that can cause mass mortalities, such as earthquakes. Here we document cascading effects of rare biogeographical (seismic) and more common ecological (temperature-related) processes on the distribution and abundances of coastal foundation species. Location Intertidal wave-exposed rocky reefs around Kaikōura, New Zealand, dominated by large, long-lived, and iconic southern bull kelps (Durvillaea antarctica and Durvillaea willana). Methods In November 2016, a 7.8 Mw earthquake uplifted the coastline around Kaikōura by up to 2 m, and a year later the region experienced the hottest summer on record. Extensive sampling of intertidal communities over 15 km coastline were done shortly after the earthquake and heatwaves and 4 years after the earthquake. Results Durvillaea lost 75% of its canopy to uplift and the heatwaves reduced canopies that had survived the uplift by an additional 35%. The survey done 4 years after the earthquake showed that Durvillaea had not recovered and that the intertidal zone in many places now was dominated by small turfs and foliose seaweed. Main conclusions Cascading impacts from seismic uplift and heatwaves have destroyed populations of Durvillaea around Kaikōura. Surviving smaller and sparser Durvillaea patches will likely compromise capacity for self-replacement and lower resilience to future stressors. These results are discussed in a global biogeographical-ecological context of seismic activity and extreme heatwaves and highlight that these events, which are not particularly rare in a geological context, may have common long-lasting ecological legacies.
Article
Full-text available
Coastal marine ecosystems are under stress, yet actionable information about the cumulative effects of human impacts has eluded ecologists. Habitat-forming seaweeds in temperate regions provide myriad irreplaceable ecosystem services, but they are increasingly at risk of local and regional extinction from extreme climatic events and the cumulative impacts of land-use change and extractive activities. Informing appropriate management strategies to reduce the impacts of stressors requires comprehensive knowledge of species diversity, abundance and distributions. Remote sensing undoubtedly provides answers, but collecting imagery at appropriate resolution and spatial extent, and then accurately and precisely validating these datasets is not straightforward. Comprehensive and long-running monitoring of rocky reefs exist globally but are often limited to a small subset of reef platforms readily accessible to in-situ studies. Key vulnerable habitat-forming seaweeds are often not well-assessed by traditional in-situ methods, nor are they well-captured by passive remote sensing by satellites. Here we describe the utility of drone-based methods for monitoring and detecting key rocky intertidal habitat types, the limitations and caveats of these methods , and suggest a standardised workflow for achieving consistent results that will fulfill the needs of managers for conservation efforts.
Article
Full-text available
Barrier sandspits are biodiverse natural features that regulate the development of lagoon systems and are popular areas for human settlement. Despite many studies on barrier island dynamics, few have investigated the impacts of sea-level rise (SLR) on sandspits. In peri-urban settings, we hypothesised that shoreline environment change would be strongly dependent on contemporary land use decisions, whilst modern engineering capabilities also present new opportunities for working with nature. Our study site in Christchurch, New Zealand, included a unique example of SLR caused by tectonic subsidence and an associated managed retreat initiative. We used a novel scenario modelling approach to evaluate both shorelines simultaneously for 0.25m SLR increments and incorporating open coast sediment supply in 25-year periods. Our key questions addressed the potential impacts of shoreline change on open coast dune and estuarine-coast saltmarsh ecosystems and implications for the role of ‘nature-based’ climate change solutions. The results identify challenges for dune conservation, with a third of the dune system eliminated in the ‘1-m SLR in 100-year’ scenario. The associated exposure of urban areas to natural hazards such as extreme storms and tsunami will likely fuel demand for seawalls unless natural alternatives can be enabled. In contrast, the managed retreat initiative on the backshore presents an opportunity to restart saltmarsh accretion processes seaward of coastal defences with the potential to reverse decades of degradation. Considering both shorelines simultaneously highlights the existence of pinch-points from opposing forces that result in small land volumes above the tidal range. Societal adaptation is delicately poised between the paradigms of resisting or accommodating nature and challenged by the long perimeter and confined nature of the sandspit feature. The use of innovative policy measures in disaster recovery contexts, as highlighted here, may offer a beneficial framework for enabling nature-based solutions to climate change and natural hazards.
Technical Report
Full-text available
This report responds to a request from Marlborough District Council (MDC) for information on the coastal environment, with a particular focus on supporting the development of a bylaw to address changes in recreational use patterns that have occurred since the Kaikōura earthquake. We present a selection of information from our earthquake recovery research that has a focus on understanding the impacts and ongoing processes of change. Major impacts of the natural disaster are associated with vertical uplift of the coastal environment, although ongoing erosion and deposition processes are also important. In addition, interactions with human activities are important because they can exert strong influences on the reassembly of ecosystems which is a critical aspect of outcomes over the longer-term. Earthquake uplift caused widespread mortality of many coastal habitats and species (e.g., algal assemblages) that are adapted to a relatively specific set of conditions, often associated with characteristic locations in relation to the tidal range. In uplifted areas the intertidal zone has moved seaward leading to a physical widening of many beaches. This has provided greater opportunity for off-road vehicle access to the coast and has become particularly noticeable at headlands and other natural barriers that were previously impassable at high tide. Off-road vehicles pose threats to sensitive vegetation and wildlife unless appropriately managed. Achieving this is assisted by an understanding of the specific impacts of vehicle use, which in turn requires information on the location of sensitive areas. To ensure the best outcomes for earthquake recovery there is an urgent need to assess and respond to the new spatial patterns, and to make plans to avoid conflicts where possible. In our RECOVER (Reef Ecology and Coastal Values, Earthquake Recovery) project funded by the Ministry of Business, Innovation and Employment (MBIE) and supported by the Ministry for Primary Industries (MPI) we are collecting information on important conservation values and activities. Although research is continuing, this report provides findings that include mapping of indigenous dune system remnants, recruitment of the indigenous sand-binders spinifex (Spinifex sericeus) and pīngao (Ficinia spiralis) on uplifted beaches, distribution of red katipō (Latrodectus katipo) within earthquake-affected dune systems, distribution of banded dotterel / pohowera (Charadrius bicinctus bicinctus) nesting pairs to determine important areas, and spatial overlaps with vehicle tracking measurements along the coast. Available under an Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license
Article
Full-text available
We investigated the response of a tidal lagoon system to a unique situation of relative sea-level change induced by powerful earthquakes (up to Mw 7.1) on the east coast of New Zealand in 2010–2011. Spatiotemporal impacts were quantified using airborne light detection and ranging (LiDAR) datasets complemented by hydrodynamic modelling and evaluation of anthropogenic influences. Ground-level changes included examples of uplift and extensive subsidence (ca. 0.5 m) associated with intertidal area reductions, particularly in supratidal zones. ‘Coastal squeeze’ effects occurred where incompatible infrastructure prevented upland ecosystem movement with relative sea-level rise. Despite large-scale managed retreat, legacy effects of land-filling have reduced the reversibility of human modifications, impairing system resiliency through poor land-use design. Elsewhere, available space in the intertidal range shows that natural environment movement could be readily assisted by simple engineering techniques though is challenged by competing land-use demands. Quantification of gains and losses showed that lagoon expansion into previously defended areas is indeed required to sustain critical habitats, highlighting the importance of a whole-system view. Identifiable coastal planning principles include the need to assess trade-offs between natural and built environments in the design of hazard management plans, requiring greater attention to the natural movement of ecosystems and areas involved. Treating these observations as a scenario illustrates the mechanisms by which coastal squeeze effects may develop under global sea-level rise, but our purpose is to help avoid them by identifying appropriate human responses. We highlight the need for an improved focus on whole-system resilience, and the importance of disaster recovery processes for adaptation to climate change.
Article
The 2016 Mw7.8 Kaikōura earthquake lifted 140km of coastline on New Zealand’s South Island by up to 6.4m. This caused extensive mortality and destruction of habitat critical for early life stages of blackfoot abalone, Haliotis iris (called pāua), a species of cultural and commercial importance. The fishery for pāua was closed, at considerable financial loss to local communities. This study determined the extent to which habitats and populations of pāua survived along the coastline. With aerial imaging, the coast was categorised into broad habitats at a 10m scale. This was used to select areas for in situ assessments of pāua populations and specific habitat features at 26 sites over 1.5 years. We quantified key habitat features to identify correlates and potential drivers of pāua abundance and distribution. We found that despite extensive habitat degradation from uplift, erosion and sedimentation, abundant pāua in size classes <30mm shell length indicated successful settlement and juvenile recruitment had occurred soon after the earthquake. Pāua up to 170mm shell length had also survived in shallow habitats. A generalized linear mixed model showed that pāua were negatively influenced by the degree of uplift, and positively associated with the cover of unconsolidated layered rocks. Juvenile pāua (<85mm) abundance was greatest at sites with <2.5m of uplift. There was further recruitment 1.5 years post-earthquake and evidence of good growth of the previous year’s cohort. Despite major disruption to this coastline, there appears to be very good potential for recovery of pāua and the fishery.
Article
Vegetated coastal ecosystems (VCEs) are in global decline and sensitive to climate change; yet may also assist its mitigation through high rates of ‘blue’ carbon sequestration and storage. Alterations of relative sea-level (RSL) are pervasive drivers of change that reflect the interaction between tidal inundation regimes and ground surface elevation. Although many studies have investigated sediment accretion within VCEs, relatively few have addressed spatiotemporal patterns of resilience in response to RSL change. In this study, we used high resolution elevation models and field surveys to identify RSL changes and socio-ecological responses in a tidal lagoon system following earthquakes in New Zealand. We expected that vegetation changes would result from RSL effects caused by surface-elevation changes in intertidal zones. Elevation measurements showed a sequence of vertical displacements resulting from major earthquakes in 2011 and 2012, and additional surface-elevation loss since. VCE losses were recorded over an 8 year period post-2011 in response to high rates of RSL rise (up to 41 mm yr⁻¹). Anthropogenic factors influenced the pattern of losses and illustrate opportunities for managing risks to other VCEs facing RSL rise. Four key principles for building VCE resilience were identified: i) anthropogenic encroachment results in resilience loss due to the need for landward migration when changes exceed the tolerance thresholds of VCEs at their lower elevational limits; ii) connectivity losses exacerbate encroachment effects, and conversely, are a practical focus for management; iii) landscape-scale risk exposure is disproportionately influenced by the largest wetland remnants illustrating the importance of site-specific vulnerabilities and their assessment; and iv) establishing new protected areas to accommodate the movement of VCEs is needed, and requires a combination of land tenure rearrangements and connectivity conservation. Embracing these concepts offers promise for improving whole-system resilience to help address the challenge of global climate change.
Article
Using micro-erosion meters (MEM) and traversing micro-erosion meters (TMEM), surface lowering rates of shore platforms on Kaikōura Peninsula, South Island, New Zealand have been measured over a total of 43 years. This record is the longest monitored network of this type. Since 1973, erosion rates have been calculated over two, two year periods 1973–1975, (n = 31) and 1993–1996, (n = 55) and at decadal scales; 1973–1993 (n = 15), 1973–2004 (n = 12), 1993–2004 (n = 46), 1993–2008 (n = 34), 1993–2016, (n = 18), 1973–2016 (n = 6). After 43 years, surface lowering rates remain similar to previously published rates at an average of 0.525 to 1.181 mm. a⁻¹. Statistical analysis shows that erosion rates over all measurement periods are derived from the same population. Thus, short term rates derived from two years of monitoring remain indicative of decadal rates of erosion. Variations between measurement periods are best explained by the loss of the more rapidly eroding bolt sites. These losses point to the difficulty of maintaining monitoring over longer time scales. A means of statistical manipulation (previously published) allows for these losses to be accounted for in determining long term rates of platform lowering. In November 2016 a Mw 7.8 earthquake raised the Kaikōura Peninsula approximately 0.8–1 m, elevating much of the shore platforms above the tide range. This earthquake has reset the MEM record ending this long running erosion monitoring site of shore platform surface lowering. However the MEM network is now being used to monitor post-earthquake response of the uplift shore platforms and new marine terraces.
Article
• The Mw 7.8 earthquake that struck the north‐east coast of the South Island of New Zealand in November 2016 caused extensive upheaval, of up to 6 m, over 110 km of coastline. Intertidal habitats were greatly affected with extensive die‐off of algal communities, high mortalities of benthic invertebrates, and greatly reduced ecosystem functioning, such as primary productivity. Only isolated pockets of key species remained in these areas, many of which were within protected areas around Kaikōura. • The loss of key species of algae and invertebrates fragmented marine populations and compromised connectivity and recovery processes because of the large dispersal distances needed to replenish populations. Severe sedimentation from terrestrial slips and erosion of newly exposed sedimentary rock compromised settlement and recruitment processes of marine species at many sites, even if distant propagules should arrive. • The combination of habitat disruption, loss of species and their functioning, and impacts on commercial fisheries, especially of abalone (Haliotis iris), requires multiple perspectives on recovery dynamics. • This paper describes these effects and discusses implications for the recovery of coastal ecosystems that include the essential involvement of mana whenua (indigenous Māori people), fishers, and the wider community, which suffered concomitant economic, recreational, and cultural impacts. These community perspectives will underpin the protection of surviving remnants of intertidal marine populations, the potential use of restoration techniques, and ultimately a successful socio‐ecological recovery.