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Remote sensing and the UN Ocean Decade: High expectations, big opportunities

Remote Sensing in Ecology and Conservation

November 2021
8(3):267-271

DOI:10.1002/rse2.241

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Authors:

Vincent Lecours

Université du Québec à Chicoutimi

M. Disney

University College London

Kate S. He

Murray State University

Nathalie Pettorelli

Zoological Society of London

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EDITORIAL

Remote sensing and the UN Ocean Decade: high

expectations, big opportunities

Vincent Lecours

, Mathias Disney

, Kate He

, Nathalie Pettorelli

, J. Marcus Rowcliffe

Temuulen Sankey

& Kylie Scales

School of Forest, Fisheries, & Geomatics Sciences, University of Florida, 7922 NW 71st St., Gainesville Florida, 32653, USA

Department of Geography, University College London, Gower Street, London WC1E 6BT, UK

Department of Biological Sciences, Murray State University, Murray Kentucky, 42071, USA

Zoological Society of London, Institute of Zoology, Regent’s Park, London NW1 4RY, UK

School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff Arizona, 86011, USA

Global-Change Ecology Research Group, University of the Sunshine Coast, Maroochydore Queensland 4556, Australia

doi: 10.1002/rse2.241

This year ofﬁcially marks the beginning of the United

Nations Decade of Ocean Science for Sustainable Devel-

opment (2021–2030)—the Ocean Decade. A primary

objective of this coordination framework is to support

scientiﬁc research and technological developments that

can contribute to the conservation and sustainable man-

agement of the world’s oceans. One of the seven Decade

Outcomes is to secure healthy and resilient oceans where

marine biodiversity is mapped and protected; however,

fulﬁlling this goal will require data, knowledge, and tech-

nology. The use of remote sensing is now established in

marine research and management and is crucial in devel-

oping our understanding of ocean patterns and processes

at multiple spatial and temporal scales (e.g., Jawak et al.,

2015). As such, remote sensing technology is expected to

play a critical role in achieving the vision set by the

Ocean Decade.

In the last 20 years, technological developments in

remote sensing have boosted our ability to monitor the

distribution and status of previously understudied ecosys-

tems, from tidal ﬂats and mangroves (Goldberg et al.,

2020; Murray et al., 2019) to continental shelves (Pygas

et al., 2020) and the deep sea (Lim et al., 2021). These

developments have also enabled the mapping of marine

physical and biogenic habitats and ecosystems at spatial

resolutions never achieved before. For example, Lyons

et al. (2020) recently demonstrated how coral reef habitats

ranging from individual reefs (~200 km

) to entire barrier

reef systems (200 000 km

) could be mapped across vast

ocean extents (>6 000 000 km

) using global multiscale

earth observations, generating high-resolution maps that

can be used to support ecosystem risk assessments and to

inform management. Deeper seaﬂoor habitats can now be

mapped and imaged at a centimeter scale using autono-

mous underwater vehicles and sensors like synthetic aper-

ture sonars (e.g., Thorsnes et al., 2019). Maps produced

by such efforts are invaluable communication tools; they

have become key for data integration and synthesis to

inform decision-making in a variety of contexts (Guisan

et al., 2013; Harris & Baker, 2020). These mapping exer-

cises can also be used to predict the distribution of spe-

cies, communities, or ecosystems based on their

associations with the physical and chemical characteristics

of the environment and can support seascape ecology

studies that relate spatial patterns with ecological pro-

cesses (Pittman, 2018).

Passive sensors mounted on unoccupied aerial vehicles

(UAVs) and satellites are commonly used to map and

monitor characteristics and components of the marine

environment, such as sea surface temperature, salinity,

marine mammal distribution, primary productivity, and

harmful algal blooms (Pettorelli, 2019). Satellite radar

altimeters have also long been used to study the oceans

and derive coarse-scale digital bathymetric models (e.g.,

Dixon et al., 1983). The information compiled by differ-

ent sensors can then be integrated to delineate broad

marine biogeographic units such as ecoregions (e.g., Sayre

et al., 2017; Spalding et al., 2007). At ﬁner scales, UAV-

mounted lidar sensors have enabled increased above-

ground biomass monitoring in coastal systems such as

mangroves (e.g., Qiu et al., 2019), while bathymetric lidar

systems have boosted data collection efforts in submerged

coastal areas, where it is often too dangerous and resource

intensive to collect acoustic data and challenging for radar

altimeters to differentiate land from water (Sandwell

et al., 2002).

While active underwater cameras mounted on remotely

operated vehicles or towed or dropped platforms have

been extensively used to collect species and seaﬂoor data

and create photomosaics of the seaﬂoor (e.g., Jones, 2009;

Sward et al., 2021), optical remote sensing is usually lim-

ited to shallow and optically clear waters. This means

ª2021 The Authors. Remote Sensing in Ecology and Conservation published by John Wiley & Sons Ltd on behalf of Zoological Society of London.

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and

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267

that, in most situations, acoustic remote sensing repre-

sents the most effective source of data for ecologists inter-

ested in marine biodiversity. Acoustic remote sensing can

be passive (i.e., using hydrophones to capture sounds in

the environment) or active (i.e., using sonars that pro-

duce directional sound and listen for returns); both have

their place in support of marine ecology and conserva-

tion. For example, multibeam echosounders enable the

production of high-resolution digital bathymetric models,

from which different terrain attributes (e.g., slope, rugos-

ity) known to be direct or indirect surrogates of species

distributions can be derived (Lecours et al., 2015,2016;

McArthur et al., 2010). Multibeam backscatter data and

sidescan sonar imagery can also provide information

about the distribution of sediment and seaﬂoor habitat

characteristics important to many species. Most often

used in ﬁsheries, singlebeam echosounders can provide

critical information about what lives in the water column,

while passive acoustic remote sensing can contribute spe-

cies occurrence and distribution data and inform abun-

dance and behavioral research (Stowell & Sueur, 2020).

There is no doubt that the UN Ocean Decade will pro-

vide exciting opportunities for the ﬁeld of remote sensing

and its applications to marine and coastal environments.

Active acoustic remote sensing technologies have histori-

cally been associated with military uses and the ﬁeld of

hydrography rather than with the remote sensing commu-

nity of practice; this has slowed the integration of data

processing and analysis methods that have proven effec-

tive in the study of terrestrial environments. This gap

offers new research opportunities that remain unexplored

in marine environments. For example, because raw multi-

beam echosounder data are displayed as point clouds that

share many characteristics with lidar point clouds,

Table 1. A meta-analysis of original research articles published in Remote Sensing in Ecology and Conservation highlights an increase in coastal

and marine studies and a strong reliance on optical remote sensing and, to a lesser extent, passive acoustics.

References Topics Remote sensing approaches

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biodiversity

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Schroeder et al. (2020) Nearshore kelp beds monitoring Satellite multispectral imagery

Cubaynes et al. (2020) Measuring whale skin spectral reﬂectance Spectroradiometer

Ridge et al. (2020) Intertidal oyster reefs mapping UAV imagery

Lyons et al. (2020) Coral reef mapping Satellite multispectral imagery, airborne hyperspectral sensor,

satellite-derived bathymetry, bathymetric data compilations

Soto et al. (2021) Estimating animal density in three

dimensions

Theoretical passive acoustic detectors and cameras

Ellis et al. (2021) Marine habitat mapping UAV imagery

Aldous et al. (2021) Coastal wetland mapping Satellite multispectral imagery and radar data, UAS imagery

Fretwell and Trathan (2021) Coastal emperor penguins colony

mapping

Satellite multispectral imagery

Ventura et al. (2021) Characterization of underwater worm

colonies

Underwater multispectral sensor

Poursanidis et al. (2021) Marine habitat mapping Satellite multispectral imagery, satellite-derived bathymetry,

underwater camera

Sward et al. (2021) Producing density estimates for the long

spined urchin

Stereo video from a remotely operated vehicle, archived

multibeam bathymetric data

Articles are listed chronologically.

268 ª2021 The Authors. Remote Sensing in Ecology and Conservation published by John Wiley & Sons Ltd on behalf of Zoological Society of London.

Editorial V. Lecours

acoustic data processing workﬂows might beneﬁt from

algorithms developed for processing lidar data. The oppo-

site is also true; the commonly used CUBE (Combined

Uncertainty and Bathymetry Estimator) algorithm for the

generation of digital bathymetric models and the com-

bined storage of bathymetry and uncertainty layers within

a single BAG (Bathymetric Attributed Grid) ﬁle format

may beneﬁt other types of remotely sensed data like lidar-

derived digital surface and terrain models. Data fusion

techniques offer opportunities for the production of

seamless digital surface models spanning the terrestrial

and marine environments that combine both optical and

acoustic remotely sensed data (e.g., Linklater et al., 2018).

New developments in image processing tools, analytical

methods like object-based image analysis, and artiﬁcial

intelligence have the potential to enhance marine ecology

and seascape ecology research (Pittman et al., 2021). New

ways to study the marine environment, such as multi-

beam water column data (e.g., Schimel et al., 2020), mul-

tispectral acoustic systems (e.g., Brown et al., 2019), and

satellite-derived bathymetry (Ashphaq et al., 2021), high-

light the need for more research into how remote sensing

can contribute to the understanding and conservation of

the world’s oceans.

The issues targeted by the Ocean Decade, such as cli-

mate change and unsustainable exploitation of marine

resources, are global and, as such, will require collabora-

tive efforts and data from around the world. However,

both ocean science and remote sensing capacities are

unevenly distributed. Mapping marine ecosystems and

biodiversity in places or through organizations that can-

not count on well-funded initiatives must rely on existing,

publicly available datasets such as the GEBCO (General

Bathymetric Chart of the Oceans) global bathymetric

dataset, archived satellite imagery, or marine biodiversity

datasets like those compiled on OBIS (Ocean Biodiversity

Information System). This highlights the need for open-

source multidisciplinary data in both remote sensing and

the marine sciences that can be spatially integrated accu-

rately; it also highlights the need for a common platform

where information gathered by these communities can be

shared and scientiﬁc agendas synchronized. Since its

inception, the editorial board of Remote Sensing in Ecology

and Conservation has welcomed contributions to coastal

and marine ecology and conservation that rely on remote

sensing (Pettorelli et al., 2015). In 2017, the editorial

board made it a goal to increase their engagement with

communities working in marine systems and acoustic

remote sensing (Pettorelli et al., 2017). The number of

published “original research” articles on coastal or marine

environments has steadily increased every year since 2016,

reaching 21% of all contributions in 2020 (Table 1).

However, the use of active acoustic remote sensing is still

underrepresented, with only one article published since

the launch of our journal. With efforts like the Seabed

2030 Project, which aims to map the world’s seaﬂoor by

2030 and relies heavily on acoustic remote sensing tech-

nologies (Mayer et al., 2018), we expect the availability of

seaﬂoor data to increase and, with them, the opportuni-

ties to better understand the ecology of our seas and

oceans. We thus want to reiterate our commitment to

marine remote sensing developments and applications

and hope that the increased opportunities will be reﬂected

in the submissions to come.

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Sep 2023

Blue carbon ecosystems (BCEs), such as mangroves, saltmarshes, and seagrasses, are increasingly recognized as natural climate solutions. Evaluating the current extent, losses, and gains of BCEs is crucial to estimating greenhouse gas emissions and supporting policymaking. Remote sensing approaches are uniquely suited to assess the factors driving BCEs dynamics and their impacts at various spatial and temporal scales. Here, we explored trends in the application of remote sensing in blue carbon science. We used bibliometric analysis to assess 2193 published papers for changes in research focus over time (1990 – June 2022). Over the past three decades, publications have steadily increased, with an annual growth rate of 16.9%. Most publications focused on mangrove ecosystems and used the optical spaceborne Landsat mission, presumably due to its long‐term, open‐access archives. Recent technologies such as LiDAR, UAVs, and acoustic sensors have enabled fine‐scale mapping and monitoring of BCEs. Dominant research topics were related to mapping and monitoring natural and human impacts on BCEs, estimating vegetation and biophysical parameters, machine and deep learning algorithms, management (including conservation and restoration), and climate research. Based on corresponding author affiliations, 80 countries contributed to the field, with United States (27.2%), China (15.0%), Australia (7.5%), and India (6.0%) holding leading positions. Overall, our results reveal the need to increase research efforts for seagrasses, saltmarshes, and macroalgae, integrate technologies, increase the use of remote sensing to support carbon accounting methodologies and crediting schemes, and strengthen collaboration and resource sharing among countries. Rapid advances in remote sensing technology and decreased image acquisition and processing costs will likely enhance research and management efforts focused on BCEs.

Integrating a conceptual framework for the sustainable development goals in the mangrove ecosystem: A systematic review

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Jul 2023

Mangrove forests are highly productive wetlands and provide essential ecosystem services for the well-being of human communities, with the Ramsar Convention being the main international agreement for planning conservation strategies for these areas of great international relevance. The present study carried out a systematic review to envision a conceptual framework on the alignment of these strategies with sustainable development (SD) and its objectives (SDGs), based on the identification of ecosystem services and their possible threats related to mangrove forest in the Ramsar classification. The study was carried out using the PSALSAR (Protocol-Search-Appraisal-Synthesis-Analysis-Report) framework and an open-access database, where the search for studies was not restricted to Ramsar Sites only. Since 1991, interest in questions about sustainable development in mangrove areas has increased, almost a decade after the first article was registered in search databases and repositories on this topic. The main SDGs addressed are related to SDG 13 (Action on Global Climate Change; 30%) and SDG 14 (Life in Water; 3%), while the goals with low performance in countries that have mangrove forests are: SDG 1 (No Poverty), SDG 2 (Zero Hunger), SDG 8 (Decent Work), SDG 13 (Climate Change), SDG 14 (Life in Water), and SDG 15 (Life on Land). However, it is still necessary to fill gaps in knowledge about the role of mangroves in the SDGs through the systematization of methods and the use of indicators that capture the socio-ecological dimensions, in order to assist in the evaluation of the SD. This requires a conceptual framework with five key elements, knowing the plan of the 2030 Agenda, SDG implementation based on ecosystem services and threats, collection and monitoring of data of the SDGs, promoting transparent and decentralized governance, and effectiveness SDGs in all countries based on the science-policy interface, which address the SDGs in this ecosystem to comply with the Ramsar Sites Strategic Plan and the 2030 Agenda, both based on the ecosystem services offered by mangroves, in order to address the identified threats and create a set of indicators for the purpose of monitoring the SDGs in relation to this ecosystem.

The Reef Environment Centralized InFormation System (RECIFS) : An integrated geo‐environmental database for coral reef research and conservation

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Full-text available

Mar 2023
GLOBAL ECOL BIOGEOGR

Motivation: Host to intricate networks of marine species, coral reefs are among the most biologically diverse ecosystems on Earth. Over the past few decades, major degradations of coral reefs have been observed worldwide, which is largely attributed to the effects of climate change and local stressors related to human activities. Now more than ever, characterizing how the environment shapes the dynamics of the reef ecosystem (e.g., shifts in species abundance, community changes, emergence of locally adapted populations) is key to uncovering the environmental drivers of reef degradation, and developing efficient conservation strategies in response. To achieve these objectives, it is pivotal that environmental data describing the processes driving such ecosystem dynamics, which occur across specific spatial and temporal scales, are easily accessible to coral reef researchers and conservation stakeholders alike. Main types of variable contained : Multiple environmental variables characterizing various facets of the reef environment, including water chemistry and physics (e.g., temperature, pH, chlorophyll concentration), local anthropogenic pressures (e.g., boat traffic, distance from agricultural or urban areas) and sea currents patterns. Spatial location and grain: Worldwide reef cells of 5 by 5 km. Time period and grain: Last 3–4 decades, monthly and yearly resolution. Major taxa and level of measurement: Environmental data important for coral reefs and associated biodiversity. Software format: Interactive web application available at https://recifs.epfl.ch.

Urban rendezvous along the seashore: Ports as Darwinian field‐labs for studying marine evolution in the Anthropocene

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Jul 2022
EVOL APPL

Humans have built ports on all the coasts of the world, allowing people to travel, exploit the sea, and develop trade. The proliferation of these artificial habitats and the associated maritime traffic are not predicted to fade in the coming decades. Ports share common characteristics: species find themselves in novel singular environments, with particular abiotic properties ‐e.g., pollutants, shading, protection from wave action‐ within novel communities in a melting‐pot of invasive and native taxa. Here we discuss how this drives evolution, including setting‐up of new connectivity hubs and gateways, adaptive responses to exposure to new chemicals or new biotic communities, and hybridization between lineages that would have never come into contact naturally. There are still important knowledge gaps however, such as the lack of experimental tests to distinguish adaptation from acclimation processes, the lack of studies to understand the putative threats of port lineages to natural populations, or to better understand the outcomes and fitness effects of anthropogenic hybridization. We thus call for further research examining “biological portuarization”, defined as the repeated evolution of marine species in port‐ecosystems under human‐altered selective pressures. Furthermore, we argue that ports act as giant mesocosms often isolated from the open sea by seawalls and locks, and so provide replicated life‐size evolutionary experiments essential to support predictive evolutionary sciences.

Regional estimates of a range‐extending ecosystem engineer using stereo‐imagery from ROV transects collected with an efficient, spatially balanced design

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Jul 2021

The redistribution of marine ecosystem engineers in response to changing climate is restructuring endemic benthic communities globally. Therefore, developing and implementing efficient monitoring programs across the complete depth range of these marine ecosystem engineers is often an urgent management priority. Traditionally, many monitoring programs have been based on a systematically selected set of survey locations that, while able to track trends at those sites through time, lack inference for the overall region being monitored. This study trialled a probabilistic sampling design to address this need, taking advantage of an important prerequisite for such designs, extensive multibeam echosounder (MBES) mapping, to inform a spatially balanced sample selection. Here, we allocated 170 remotely operated vehicles (ROVs) transects based on a spatially balanced probabilistic sampling design across three locations with extensive mapping. Generalized additive models were used to estimate the density and associated barren cover of the range‐expanding ecosystem engineer, the long spined urchin (Centrostephanus rodgersii). Estimates were generated at a reef‐wide scale across three locations on the east coast of Tasmania, Australia, representing the leading edge of the species recent range extension. Model‐based estimates of urchin density and barren cover incorporated seabed structure attributes, such as depth and ruggedness, with differences in these modelled relationships being identified between locations. Estimates ranged from 0.000065 individuals m−2 and 0.018% barren cover in the Tasman Peninsula to 0.167 individuals m−2 and 2.10% barren cover at Governor Island Marine Reserve, reflecting a north to south distributional gradient. This study highlights the value of combining probabilistic sampling designs, ROV transects, stereo video, and MBES mapping to generate reliable and robust estimates of important ecosystem species needed to protect reef‐based fishery and conservation values via adaptive and informed management. Many marine monitoring programs are based on systematically selected set of survey locations that, while able to track trends at those sites through time, lack inference for the overall region being monitored. This study trialled a probabilistic sampling design to address this need, taking advantage of an important prerequisite for such designs, extensive multibeam echosounder mapping, to inform a spatially balanced sample. Precise model estimates of urchin density and barren habitat were possible, highlighting the value of combining probabilistic sampling designs, remotely operated vehicle transects, stereo video, and fine‐scale mapping to generate reliable and robust estimates of important ecosystem species, which are needed to protect reef‐based fishery and conservation values via adaptive and informed management.

Review of near-shore satellite derived bathymetry: Classification and account of five decades of coastal bathymetry research

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Mar 2021

The number of civilian, commercial and military applications are dependant on accurate knowledge of bathymetry of coastal regions. Conventionally, hydrographic surveying methods are used for bathymetric surveys carried by ship-based acoustic systems, but needs high-cost resources. Space technology has provided a cost-effective alternate means for charting near shore and inaccessible waters. The optical satellite data have capabilities to offer alternate solution in near-shore region, which has been researched for past 50 years, using evolving algorithms to estimate Satellite Derived Bathymetry (SDB). However, there is no agreement on use of terms like approach, model, method and techniques, which have been used varyingly and interchangeably as per context of SDB research. This paper suggests a classification scheme for SDB algorithms which is also applicable to other Marine Remote Sensing studies. In this paper, based on literature available on SDB for the past five decades, an insight on SDB classification has been offered grounded in research philosophy. The SDB Approaches, models, methods and techniques have been elaborated with chronological development, along with SDB studies based on them, their accuracy and errors in SDB retrieval. We have suggested a matrix of prerequisite satellite data, in-situ data resolution, methods and algorithms of SDB based on level of accuracy needs to be achieved, which will guide future researchers to select one as per their context of research.

Seascape ecology: Identifying research priorities for an emerging ocean sustainability science

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Apr 2021

Seascape ecology, the marine-centric counterpart to landscape ecology, is rapidly emerging as an interdisciplinary and spatially explicit ecological science with relevance to marine management, biodiversity conservation and restoration. While important progress in this field has been made in the past decade, there has been no coherent prioritisation of key research questions to help set the future research agenda for seascape ecology. We used a two-stage modified Delphi method to solicit applied research questions from academic experts in seascape ecology and then asked respondents to identify priority questions across nine interrelated research themes using two rounds of selection. We also invited senior management/conservation practitioners to prioritise the same research questions. Analyses highlighted congruence and discrepancies in perceived priorities for applied research. Themes related to both ecological concepts and management practice, and those identified as priorities include seascape change, seascape connectivity, spatial and temporal scale, ecosystem-based management, and emerging technologies and metrics. Highest priority questions (upper tercile) received 50% agreement between respondent groups and lowest priorities (lower tercile) received 58% agreement. Across all three priority tiers, 36 of the 55 questions were within a ±10% band of agreement. We present the most important applied research questions as determined by the proportion of votes received. For each theme, we provide a synthesis of the research challenges and the potential role of seascape ecology. These priority questions and themes serve as a roadmap for advancing applied seascape ecology during, and beyond, the UN Decade of Ocean Science for Sustainable Development (2021–2030).

Cold-Water Coral Habitat Mapping: Trends and Developments in Acquisition and Processing Methods

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Full-text available

Jan 2021

Cold-water coral (CWC) habitats are considered important centers of biodiversity in the deep sea, acting as spawning grounds and feeding area for many fish and invertebrates. Given their occurrence in remote parts of the planet, research on CWC habitats has largely been derived from remotely-sensed marine spatial data. However, with ever-developing marine data acquisition and processing methods and non-ubiquitous nature of infrastructure, many studies are completed in isolation resulting in large inconsistencies. Here, we present a concise review of marine remotely-sensed spatial raster data acquisition and processing methods in CWC habitats to highlight trends and knowledge gaps. Sixty-three studies that acquire and process marine spatial raster data since the year 2000 were reviewed, noting regional geographic location, data types (‘acquired data’) and how the data were analyzed (‘processing methods’). Results show that global efforts are not uniform with most studies concentrating in the NE Atlantic. Although side scan sonar was a popular mapping method between 2002 and 2012, since then, research has focused on the use of multibeam echosounder and photogrammetric methods. Despite advances in terrestrial mapping with machine learning, it is clear that manual processing methods are largely favored in marine mapping. On a broader scale, with large-scale mapping programs (INFOMAR, Mareano, Seabed2030), results from this review can help identify where more urgent research efforts can be concentrated for CWC habitats and other vulnerable marine ecosystems.

Cloud-native Seascape Mapping of Mozambique’s Quirimbas National Park with Sentinel-2

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Full-text available

Nov 2020

The lack of detailed spatial information on coastal resources, notably shallow water coral reefs and associated benthic habitats, impedes our ability to protect and manage them in the face of global climate change and anthropogenic impacts. Here, we develop a semi‐automated workflow in the cloud that uses freely available Sentinel‐2 data from the European Space Agency (ESA) Copernicus programme to derive information on near‐shore coral reef habitats in the Quirimbas National Park (QNP), a recently declared biosphere reserve in northern Mozambique. We use an end‐to‐end cloud‐based framework within the Google Earth Engine cloud geospatial platform to process imagery from raw pixels to cloud‐free composites which are corrected for glint and surface artefacts, water column and derived estimated depth and then classified into four benthic habitats. Using independent training and validation data, we apply three supervised classification algorithms: random forests (RF), support vector machine (SVM) and classification and regression trees (CART). Our results show that random forests are the most accurate supervised algorithm with over 82% overall accuracy. We mapped over 105 000 ha of shallow water habitat inside the protected area, of which 18% are dominated by coral and hardbottom; 27.5% are seagrass and submerged aquatic vegetation and another 23.4% are soft and sandy substrates, and the remaining area is optically deep water. We employ satellite‐derived bathymetry to assess slope, bathymetric position, rugosity and underwater topography of these habitats. Finally, a spectral unmixing model provides further sub‐pixel–level information of habitats with the potential to monitor changes over time. This effort provides the first, consistent and repeatable and also scalable coastal information system for an east African tropical marine protected area, which hosts shallow‐water ecosystems which are of great significance to local communities and building resilience towards climate change.

Integration of close-range underwater photogrammetry with inspection and mesh processing software: a novel approach for quantifying ecological dynamics of temperate biogenic reefs Introduction and Background

Article

Full-text available

Oct 2020

Abstract Characterizing and monitoring changes in biogenic 3‐dimensional (3D) structures at multiple scales over time is challenging within the practical constraints of conventional ecological tools. Therefore, we developed a structure‐from‐motion (SfM)‐based photogrammetry method, coupled with inspection and mesh processing software, to estimate important ecological parameters of underwater worm colonies (hummocks) constructed by the sabellariid polychaete Sabellaria alveolata, using non‐destructive, 3D modeling and mesh analysis. High resolution digital images of bioconstructions (hummocks) were taken in situ under natural conditions to generate digital 3D models over different sampling periods to analyse the morphological evolution of four targeted hummocks. 3D models were analysed in GOM Inspect software, a powerful and freely available mesh processing software to follow growth as well as morphology changes over time of each hummock. Linear regressions showed 3D models only slightly overestimated the real dimensions of the reference objects with an average error

Discovery of new colonies by Sentinel2 reveals good and bad news for emperor penguins

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Aug 2020

The distribution of emperor penguins is circumpolar, with 54 colony locations currently reported of which 50 are currently extant as of 2019. Here we report on eight newly discovered colonies and confirm the rediscovery of three breeding sites, only previously reported in the era before Very High Resolution satellite imagery was available, making a total of 61 breeding locations. This represents an increase of ~20% in the number of breeding sites, but, as most of the colonies appear to be small, they may only increase the total population by around 5–10%. The discoveries have been facilitated by the use of Sentinel2 satellite imagery, which has a higher resolution and more efficient search mechanism than the Landsat data previously used to search for colonies. The small size of these new colonies indicates that considerations of reproductive output in relation to metabolic rate during huddling is likely to be of interest. Some of the colonies exist in offshore habitats, something not previously reported for emperor penguins. Comparison with recent modelling results show that the geographic locations of all the newly found colonies are in areas likely to be highly vulnerable under business‐as‐usual greenhouse gas emissions scenarios, suggesting that population decreases for the species will be greater than previously thought. Sentinel2 enables us to track and discover emperor penguin colonies. We use the new technology to discover 11 new colony sites, increasing the number of known colonies by 20%. However, it is not all good news for emperors, as all the newly found colonies are in areas vulnerable to future sea ice loss, and the new discoveries actually make the species more vulnerable to climate change than previously thought.

Ecoacoustics: acoustic sensing for biodiversity monitoring at scale

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Aug 2020

Global declines in human‐driven mangrove loss

Article

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Jul 2020

Global mangrove loss has been attributed primarily to human activity. Anthropogenic loss hotspots across Southeast Asia and around the world have characterized the ecosystem as highly threatened, though natural processes such as erosion can also play a significant role in forest vulnerability. However, the extent of human and natural threats has not been fully quantified at the global scale. Here, using a Random Forest‐based analysis of over one million Landsat images, we present the first 30‐meter resolution global maps of the drivers of mangrove loss from 2000‐2016, capturing both human‐driven and natural stressors. We estimate that 62% of global losses between 2000‐2016 resulted from land‐use change, primarily through conversion to aquaculture and agriculture. Up to 80% of these human‐driven losses occurred within six Southeast Asian nations, reflecting the regional emphasis on enhancing aquaculture for export to support economic development. Both anthropogenic and natural losses declined between 2000‐2016, though slower declines in natural loss caused an increase in their relative contribution to total global loss area. We attribute the decline in anthropogenic losses to the regionally‐dependent combination of increased emphasis on conservation efforts and a lack of remaining mangroves viable for conversion. While efforts to restore and protect mangroves appear to be effective over decadal time scales, the emergence of natural drivers of loss presents an immediate challenge for coastal adaptation. We anticipate that our results will inform decision making within conservation and restoration initiatives by providing a locally‐relevant understanding of the causes of mangrove loss.

Influence of altitude on tropical marine habitat classification using imagery from fixed‐wing, water‐landing UAVs

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May 2020

Unmanned aerial vehicles (UAVs) are cost‐effective remote sensing tools useful for generating very high‐resolution (VHR) aerial imagery. Habitat maps generated from UAV imagery are a fundamental component of marine spatial planning, essential for the designation and governance of marine protected areas (MPAs). We investigated whether UAV survey altitude affects habitat classification performance and the classification accuracy of thematic maps from a tropical shallow water environment. We conducted repeated UAV flights at 75, 85, and 110 m, using a fixed‐wing UAV on the Turneffe Atoll, Belize. Flights were ground truthed with snorkel surveys. Images were mosaiced to form orthomosaics and transformed into thematic maps through semi‐automatic object‐based image analysis (OBIA). Three subset areas (4000 m2, 17 000 m2 and 17 000 m2) from two cayes on the atoll were selected to investigate the effect of survey altitude. A linear regression demonstrated that for every 1 m increase in survey altitude, there was a ~1% decrease in the overall classification accuracy. A low survey altitude of 75 m produced a higher classification accuracy for thematic maps and increased the representation of mangrove, seagrass and sand. The variability in classified cover was driven by altitude, although the direction and extent of this relationship was specific to each class. For coral and sea, classified cover decreased with increased altitude. Mangrove classified cover was non‐sensitive to altitude changes, demonstrating a lesser need for a consistent survey altitude. Sand and seagrass had a greater sensitivity to altitude, due to classified cover variability between altitudes. Our findings suggest that survey altitude should be minimized when classifying tropical marine environments (coral, seagrass) and, given that most fixed‐wing UAVs are restricted to a minimum altitude of 70 m, we recommend an altitude of 75 m. Survey altitude should be a major consideration when targeting habitats with greater sensitivity to altitude variability. A fixed‐wing unmanned aerial vehicle (UAV) was operated to acquire very high‐resolution aerial imagery of two cayes on the Turneffe Atoll, Belize. Three subset areas (4000 km2, 17 000 km2 and 17 000 km2) were selected from the UAV surveys to investigate the effect of altitude on habitat classification. A linear regression demonstrated that for every 1 m increase in altitude, there was a ~1% decrease in the overall classification accuracy. A low survey altitude of 75 m produced higher classification accuracy for thematic maps, and increased the representation of mangrove, seagrass, and sand. The variability in classified cover was driven by altitude, although the direction and extent of this relationship was specific to each class. Our findings suggest that survey altitude should be minimised to 75 m when classifying tropical marine environments (coral, seagrass). A consistent altitude should be considered for surveys targeting habitats with greater sensitivity to altitude variability.