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Past and future global transformation of terrestrial ecosystems under climate change


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Impacts of global climate change on terrestrial ecosystems are imperfectly constrained by ecosystem models and direct observations. Pervasive ecosystem transformations occurred in response to warming and associated climatic changes during the last glacial-to-interglacial transition, which was comparable in magnitude to warming projected for the next century under high-emission scenarios. We reviewed 594 published paleoecological records to examine compositional and structural changes in terrestrial vegetation since the last glacial period and to project the magnitudes of ecosystem transformations under alternative future emission scenarios. Our results indicate that terrestrial ecosystems are highly sensitive to temperature change and suggest that, without major reductions in greenhouse gas emissions to the atmosphere, terrestrial ecosystems worldwide are at risk of major transformation, with accompanying disruption of ecosystem services and impacts on biodiversity.
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Past and future global transformation
of terrestrial ecosystems under
climate change
Connor Nolan
Julio L. Betancourt
, Heather A. Binney
, Simon Brewer
Brian M. Chase
, Rachid Cheddadi
Mary E. Edwards
, William D. Gosling
, Simon Haberle
, Sara C. Hotchkiss
Brian Huntley
, A. Peter Kershaw
Claudio Latorre
, Michelle Leydet
, Anne-Marie Lézine
, Kam-Biu Liu
Yao Liu
, Matt S. McGlone
, Robert A. Marchant
Arata Momohara
, Stefanie Müller
, Bette L. Otto-Bliesner
Caiming Shen
, Janelle Stevenson
, Hikaru Takahara
John Tipton
, Annie Vincens
, Chengyu Weng
Zhuo Zheng
Impacts of global climate change on terrestrial ecosystems are imperfectly
constrained by ecosystem models and direct observations. Pervasive ecosystem
transformations occurred in response to warming and associated climatic changes
during the last glacial-to-interglacial transition, which was comparable in
magnitude to warming projected for the next century under high-emission
scenarios.We reviewed 594 published paleoecological records to examine compositional
and structural changes in terrestrial vegetation since the last glacial period and
to project the magnitudes of ecosystem transformations under alternative future
emission scenarios. Our results indicate that terrestrial ecosystems are highly
sensitive to temperature change and suggest that, without major reductions in
greenhouse gas emissions to the atmosphere, terrestrial ecosystems worldwide are
at risk of major transformation, with accompanying disruption of ecosystem services
and impacts on biodiversity.
Terrestrial ecosystem function is governed
structure of vegetation (13), and climate
change impacts on vegetation can potentially
cause disruption of ecosystem services and
loss of biodiversity (4,5). It is critical to assess
the likely extent of ecosystem transformation
as global greenhouse gas (GHG) emissions in-
crease (6) and to understand the full potential
magnitude of impacts should current GHG
emission rates continue unabated.
Ecosystem transformation generally involves
the replacement of dominant plant species or
functional types by others, whether recruited
locally or migrating from afar. Observations from
around the globe indicate that current climate
change may already be driving substantial changes
in vegetation composition and structure (3). Eco-
system change is accelerated by mass mortality
of incumbent dominants (7,8), and widespread
dieback events and other large disturbances are
already under way in many forests and wood-
lands (911), with further mortality events pre-
dicted under increasing temperatures and drought
(3,9,10,12). Replacement of predisturbance
dominants by other species and growth forms
has been widely documented (8,13,14). In addi-
tion, evidence is accumulating for geographic
range shifts in individual species, and climate
change is interacting with invasive species, fire
regimes, land use, and CO
increase to drive
vegetation changes in many regions (15,16).
Beyond observations of recent and ongoing
change, models indicate ecosystem transforma-
tion under climate projections for the 21st
century. These include dynamic global veg-
etation models (3,17), species distribution
models (18), and comparison of the multivariate
climate distance between biomes with that be-
tween modern and future climates (19). However,
the capacity for assessing the magnitudes of
ecosystem transformation under future climate
scenarios is limited by the difficulty of evaluat-
ing model performance against empirical records,
particularly when projected climate states are
novel (19,20).
Paleoecological records of past ecological re-
sponses to climate change provide an independent
means for gauging the sensitivity of ecosystems
to climate change. High-precision time-series
studies indicate that local and regional ecosystems
can shift rapidly, within years to decades, under
abruptclimatechange(2123), but sites with
such detailed chronologies are scarce. In this
study, we used published reports to compile
a global network of radiocarbon-dated paleo-
ecological records of terrestrial vegetation com-
position and structure since the Last Glacial
Maximum (LGM), ~21,000 years before the pres-
ent (yr B.P.) (24). Most postglacial warming
happened 16,000 to 10,000 yr B.P., although it
commenced earlier in parts of the Southern
Hemisphere (25,26). Global warming between
the LGM and the early Holocene (10,000 yr B.P.)
was on the order of 4 to 7°C, with more warm-
ing over land than oceans (26,27). These esti-
mates are roughly comparable to the magnitude
of warming that Earth is projected to undergo
in the next 100 to 150 years if GHG emissions
are not reduced substantially (28). The magni-
tudes of changes in vegetation composition and
provide an index of the magnitude of ecosystem
change that may be expected under warming
of similar magnitude in the coming century
(29). Although the rate of projected future glob-
al warming is at least an order of magnitude
greater than that of the last glacial-to-interglacial
transition (26), a glacial-to-modern compari-
son provides a conservative estimate of the ex-
tent of ecological transformation to which the
planet will be committed under future climate
We reviewed and evaluated paleoecological
(pollen and macrofossil) records from 594 sites
Nolan et al., Science 361, 920923 (2018) 31 August 2018 1of4
Fig. 1. Vegetation differences between
the LGP and the present. Each square
represents an individual paleoecological
site. The color density indicates the magnitude
of estimated vegetation change since the
LGP (21,000 to 14,000 yr B.P.). Background
shading denotes the estimated temperature
anomaly between the LGM 21,000 years
ago and today on the basis of assimilated
proxy-data and model estimates (27).
(A) Composition. (B) Structure.
on August 30, 2018 from
worldwide (fig. S1), all drawn from peer-
reviewed published literature, to determine the
magnitude of postglacial vegetation change.
We adopted an expert-judgment approach in
which paleoecologists with relevant regional ex-
perience compiled published records (table S1);
reviewed the data, diagrams, and accompany-
ing papers; and inferred the composition and
structure of the glacial-age and Holocene veg-
etation at each site (24). For the purposes of
our analyses, we defined the LGP as the interval
between 21,000 and 14,000 yr B.P. Although
postglacial warming was under way in many
regions by 16,000 yr B.P. (25), continental ice
sheets were still extensive 14,000 yr B.P., and
some climate regimes remained essentially
glacialin nature, particularly in the Northern
Hemisphere (30). Extending the LGP window
to 14,000 yr B.P. provides a larger array of rec-
ords for the assessment, both in g lac iated an d
unglaciated terrains, and renders our analysis
more conservative (climatic and vegetation con-
trasts with the Holocene are likely to decrease
between 21,000 and 14,000 yr B.P.).
For each record, experts were asked to clas-
sify the magnitudes of compositional change and
structural change since the LGP as large, mod-
erate, or low and to provide detailed justifica-
tion for their judgments (24) (table S2). This
placed all the diverse records into a common
framework for comparison. For sites that experi-
enced moderate to large ecological change,
experts were also asked to assess the role of
driving the observed vegetation change. For
each of these four judgments, experts were asked
to state their level of confidence as high, medium,
or low. In assessing the role of climate change,
experts were asked to focus specifically on wheth-
er climate change since the LGP was sufficient
to drive the observed changes, acknowledging
that other factors (e.g., human activity, postglacial
increase, and megafaunal dynamics) may
have also played important roles. For sites with
a long history of human land use, experts used
Holocene records predating widespread land
clearance as a benchmark for comparison with
the LGP records.
Our results indicate that the magnitude of
past glacial-to-interglacial warming was suffi-
changes in vegetation composition that were
moderate (27% of sites) to large (71%), as well as
moderate (28%) to large (67%) structural changes
(Fig. 1 and table S3). These changes were par-
ticularly evident at mid- to high latitudes in the
Northern Hemisphere, as well as in southern
South America, tropical and temperate south-
ern Africa, the Indo-Pacific region, Australia,
Oceania, and New Zealand (Fig. 1A). Com-
positional change at most sites in the Neo-
tropics was moderate to large, but three sites
showed little or no compositional change, all
Nolan et al., Science 361, 920923 (2018) 31 August 2018 2of4
Fig. 2. Estimated temperature differences
for different categories of vegetation
response. Box plots of the estimated
mean annual temperature differences
between the LGM and today in each of
the three vegetation change categories
(low, moderate, and large) for
(A) composition and (B) structure.
Low vegetational changes are associated
largely with relatively small temperature
anomalies, whereas moderate and
large changes are associated
with larger post-LGM temperature
differences, indicating that the
magnitude of temperature change
plays an important role in the
magnitude of vegetation change.
The glacial temperature anomalies
are from data in (27). Analyses using
the TraCE-21ka simulation show
similar patterns (fig. S4).
Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA.
School for Environment and Sustainability, University of Michigan, Ann Arbor, MI 48109, USA.
Department of
Biosciences, University of Durham, Durham DH1 3LE, UK.
Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA.
National Research Program, U.S.
Geological Survey, Reston, VA 20192, USA.
Geography and Environment, University of Southampton, Southampton SO17 1BJ, UK.
Department of Geography, University of Utah, Salt
Department of Biological Sciences, Florida Institute of Technology, Melbourne, FL 32901, USA.
Centre National de la Recherche Scientifique, UMR 5554,
Institut des Sciences de lEvolution de Montpellier, Université Montpellier, Bat. 22, CC061, Place Eugène Bataillon, 34095 Montpellier, France.
Aix Marseille Université, Avignon
Université, CNRS, IRD, Institut Méditerranéen de Biodiversité et dEcologie, 13545 Aix-en Provence, France.
Palaeontology, Geobiology and Earth Archives Research Centre (PANGEA),
University of New South Wales, Sydney, NSW 2052, Australia.
State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences,
Xian 71002, Shaanxi, China.
College of Natural Sciences and Mathematics, University of AlaskaFairbanks, Fairbanks, AK 99775, USA.
Institute for Biodiversity and Ecosystem
Dynamics, University of Amsterdam, 1090 GE Amsterdam, Netherlands.
School of Environment, Earth and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes MK7
6AA, UK.
Department of Archaeology and Natural History, Australian National University, Canberra, Australia.
Department of Botany, University of Wisconsin, Madison, WI 53706, USA.
Department of Geosciences, Pennsylvania State University, State College, PA 16802, USA.
School of Earth, Atmosphere, and Environment, Monash University, Melbourne, VIC 3800,
Departamento de Ecología, Institute of Ecology and Biodiversity (IEB), Pontificia Universidad Católica de Chile, Santiago, Chile.
Sorbonne Université, CNRS-IRD-MNHN,
LOCEAN/IPSL Laboratory, 4 Place Jussieu, 75005 Paris, France.
Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ 86011, USA.
North-East Interdisciplinary Scientific Research Institute, Far East Branch
Russian Academy of Sciences, Magadan 685000, Russia.
Landca re Research, Lincoln 7640, New Zealand.
Department of Environment, York Institute for Tropical Ecosystems, University of York,
York YO10 5NG, UK.
Graduate School of Horticulture, Chiba University, Matsudo-shi, Chiba 271-8510, Japan.
Departamento de Ciencias Ecológicas, IEB and (CR)2, Universidad de Chile, Santiago,
Institute of Geological Sciences, Freie Universität Berlin, D-12249 Berlin, Germany.
National Center for Atmospheric Research, Climate and Global Dynamics Laboratory, Boulder, CO 80307,
Yunnan Normal University, Key Laboratory of Plateau Lake Ecology and Global Change, Kunming, Yunnan 650092, China.
School of Culture, History, and Language, Australian National
University, Canberra, Australia.
Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, 606-8522, Japan.
Department of Mathematical Sciences, University of
Arkansas, Fayetteville, AR 72701, USA.
Centre Européen de Recherche et dEnseignement des Géosciences de lEnvironnement (CEREGE), 13545 Aix-en-Provence, France.
School of Ocean and Earth
Science, Tongji University, Shanghai, China.
Institute of Nihewan Archaeology and College of Resource and Environmental Sciences, Hebei Normal University, Shijiazhuang 050024, China.
School of
Earth Science and Engineering, Guangdong Provincial Key Lab of Geodynamics and Geohazards, Sun Yat-Sen University, Guangzhou 510275, China.
Southwest Climate Adaptation Science Center, U.S.
Geological Survey, Tucson, AZ 85721, USA.
*Corresponding author. Email:
on August 30, 2018 from
with medium to high confidence (fig. S2). Shifts
in vegetation structure were also moderate to
large at mid- to high-latitude sites, although a
few sites showed low change (Fig. 1B). The Neo-
tropics had nine sites with little or no structural
change (Fig. 1B), all with high-confidence assess-
ments (fig. S2). These sites have been occupied
by tropical forest ecosystems since the LGM,
although most have undergone moderate to
large compositional change (31,32). For nearly
all sites that experienced moderate or large eco-
logical change, climate change since the LGP
was judged to be sufficient to explain the ob-
Atmospheric CO
concentrations also increased
from 190 to 280 parts per million during the
deglaciation, interacting with and in some cases
modulating ecological responses to climate
change. However, CO
changes alone cannot
account for postglacial vegetation changes (sup-
plementary text).
Independently of the expert-judgment pro-
cess, we used the estimated anomaly in mean
annual temperatures between the LGM and
the present (preindustrial) as a proxy for the
overall magnitude of climate change since the
LGP (24). LGM temperature estimates were
derived using an assimilated datamodel in-
tegration (27). Low-change sites were largely
concentrated in regions where the estimated
temperature anomaly was relatively small (Fig. 1).
To explore this relationship further, we plotted
the frequency distribution of the difference
between estimated LGM and present-day mean
annual temperatures for individual sites in
each of the three ecological-response categories.
Nearly all sites with low compositional change
between the LGP and today are associated with
small estimated temperature anomalies (median,
2.4°C), whereas sites with moderate to high
compositional change have larger temperature
anomalies (Fig. 2A). Results for structural changes
are similar, although a greater number of sites
with low structural change include larger tem-
perature anomalies (Fig. 2B). This difference
is not surprising, because compositional change
in vegetation can occur without an accompany-
ing change in vegetation structure (Fig. 1). Europe
and eastern North America experienced un-
usually large temperature changes since the
LGM, owing to depressed temperatures near
the large ice sheets, and these regions show
substantial compositional and structural changes
since the LGP. However, results from other parts
of the globe indicate that widespread ecosystem
ature changes (fig. S3). We repeated our anal-
ysis using the TraCE-21ka model simulations
(33,34), which yield a lower magnitude of LGP-
to-Holocene climate change (35); despite the
potential conservative bias, results for com-
positional and structural changes (fig. S4) were
similar to those in Fig. 2. Temperature dif-
ferences between the LGP and the present were
substantially greater for sites with large eco-
logical change than for those with low to mod-
erate change, by both paleoclimate estimates
(27,33) (table S2).
We also used our database of ecological change
since the LGM to assess the global distribution
of the probabilities of large compositional and
structural changes given GHG emission scenar-
ios [representative concentration pathways (RCPs)
2.6, 4.5, 6.0, and 8.5, each as simulated by the
Community Climate System Model version 4
(CCSM4)] (24,36). The range of LGM-to-present
temperature changes (Fig. 2) overlaps with the
range of temperature changes projected for the
coming century under these scenarios (Fig. 3A
and fig. S5). We quantified the relationship be-
tween temperature and ecological change by
using a logistic spline regression with ordered
categories (37). We fit models for compositional
and structural change by using the temperature
change since the LGM as the independent pre-
dictor variable. In both models, LGM-to-modern
ecosystem change (P< 0.001). We then used
these models to predict the risk of large change
for the future range of projected global temper-
ature changes (Fig. 3B) and to map the prob-
ability of large change under RCP 2.6 and RCP
8.5 (Fig. 3, C to F) at the end of the 21st
Nolan et al., Science 361, 920923 (2018) 31 August 2018 3of4
Fig. 3. Estimated vegetation change under future climate scenarios. (A) Box plots
of the estimated mean annual temperature differences between today and future climate
simulations for individual sites (as determined by using the nearest grid point). Most
sites show relatively small temperature change under the low-emission scenario (RCP 2.6),
with substantially greater change under the high-emission scenario (RCP 8.5). (B) Probabilities
of large changes in vegetation composition and structure as a function of temperature
change. (Cto F) Estimated probabilities of large compositional and structural changes by
the end of the 21st century (the average of the period from 2081 to 2100) under RCP 2.6
(C and E) and RCP 8.5 (D and F). Probabilities (B to F) are estimated from a logistic spline
regression model fit by using LGM-to-modern temperature change as a predictor variable
and observed LGP-to-modern vegetation changes (large versus not large) as the response
variable. Future temperature increases are calculated as an average for 2081 to 2100
under the model scenarios, minus an average for 1985 to 2005 from the CCSM4 historical
simulation. Analyses using the TraCE-21ka simulation show similar patterns (fig. S7).
on August 30, 2018 from
century (see fig. S6 for RCP 4.5 and RCP 6.0).
Under RCP 2.6, the probability of large compo-
sitional change is less than 45% over most of
the globe (Fig. 3C) and the probability of large
structural change is generally less than 30%
(Fig. 3E). By contrast, under the business- as-
usual emissions scenario, RCP 8.5, the proba-
bilities of large compositional change and large
structural change are both greater than 60%
(Fig. 3, D and F). Analyses using the TraCE-
21ka model yielded similar patterns (fig. S7).
Our study uses a single variable, mean annual
temperature, as a metric for the broader array
of climatic changes that can drive vegetation
change, and it compares vegetation and climate
states separated by 10,000 to 20,000 years. Fu-
ture climate change, like that in the past, will
be multivariate, involving shifts in seasonal tem-
peratures, seasonal precipitation, climate extremes,
and variability regimes. As mean annual tem-
perature increases, other ecologically important
variables will change, often in complex or counter-
intuitive ways (20,38,39), and ecological responses
will often be episodic or nonlinear (8,1315).
Although the temperature increases since the
LGP provide crude analogs for ongoing and
future climate changesfor example, boundary
conditions and forcings are different now
(26,40,41)our results nevertheless provide
concrete evidence that vegetation composition
and structure are sensitive to changes in mean
annual temperature of the magnitudes forecast
for the coming century and that vegetation
transformations will become increasingly exten-
sive as temperatures increase. Under the RCP
8.5 scenario, the rate of warming will be on the
order of 65 times as high as the average warm-
ing during the last deglaciation (26). Further-
more, the warming between the LGP and the
Holocene occurred within the range of previous
glacial and interglacial temperatures, whereas
projected future changes will exceed those ex-
perienced over the past 2 million years (26).
Although many ecological responses (e.g., species
migration, colonization, and succession) will
likely lag behind climate changes, ecosystem
transformations will often be accelerated by
disturbance and mortality events, land use, and
invasive species (715).
We therefore conclude that terrestrial veg-
etation over the entire planet is at substantial
risk of major compositional and structural
GHG emissions. Much of this change could
occur during the 21st century, especially where
vegetation disturbance is accelerated or amp-
lified by human impacts (7). Many emerging
ecosystems will be novel in composition, struc-
ture, and function (42), and many will be
ephemeral under sustained climate change;
equilibrium states may not be attained until
the 22nd century or beyond. Compositional
transformation will affect biodiversity via dis-
integration and reorganization of communities,
replacement of dominant or keystone species,
pass-through effects on higher trophic lev-
els, and ripple effects on species interactions (16,43).
Structural transformation will have particularly
large consequences for ecosystem services (4),
including the achievement of nature-based
development solutions under the United Na-
tionsSustainable Development Goals (44).
Structural changes will also influence bio-
diversity, driving alterations in habitats and
resources for species at higher trophic levels.
Compositional and structural changes may
also induce potentially large changes to car-
bon sources and sinks, as well as to atmo-
spheric moisture recycling and other climate
feedbacks. Our results suggest that impacts
on planetary-scale biodiversity, ecological func-
tioning, and ecosystem services will increase
substantially with increasing GHG emissions,
particularly if warming exceeds that projected
by the RCP 2.6 emission scenario (1.5°C).
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The paper benefitted from the thoughtful comments of
S. T. Gray and three anonymous reviewers. Funding:
This research was supported by the NSF (DEB-1241851,
AGS-1243125, and EAR-1304083) and by the Department
of the Interiors Southwest Climate Adaptation Science
Center. Research in northeast Siberia was funded by
the Russian Academy of Sciences, FEB (15-I-2-067),
and the Russian Foundation for Fundamental Research
(15-05-06420). Author contributions: S.T.J., C.N.,
and J.T.O. designed the project; all authors collected
data; C.N. analyzed data with advice from J.T.O., S.T.J.,
S.B.,and J.T.;andS.T.J.,C.N.,andJ.T.O.wrote the
paper with text contributions in the supplementary
materials from B.M.C., M.B.B., M.E.E., J.L.B., B.H., Y.L.,
and S.J.I. and further contributions from all authors.
Competing interests: Theauthorsdeclarenocompeting
interests. Data and materials availability: All data
are available in the main text or the supplementary
Materials and Methods
Supplementary Text
Figs. S1 to S8
Tables S1 to S4
References (4595)
Data S1
27 April 2017; resubmitted 24 April 2018
Accepted 30 July 2018
Nolan et al., Science 361, 920923 (2018) 31 August 2018 4of4
on August 30, 2018 from
Past and future global transformation of terrestrial ecosystems under climate change
Pavel E. Tarasov, John Tipton, Annie Vincens, Chengyu Weng, Qinghai Xu, Zhuo Zheng and Stephen T. Jackson
Momohara, Patricio I. Moreno, Stefanie Müller, Bette L. Otto-Bliesner, Caiming Shen, Janelle Stevenson, Hikaru Takahara,
Michelle Leydet, Anne-Marie Lézine, Kam-Biu Liu, Yao Liu, A. V. Lozhkin, Matt S. McGlone, Robert A. Marchant, Arata
Gosling, Simon Haberle, Sara C. Hotchkiss, Brian Huntley, Sarah J. Ivory, A. Peter Kershaw, Soo-Hyun Kim, Claudio Latorre,
Brewer, Mark B. Bush, Brian M. Chase, Rachid Cheddadi, Morteza Djamali, John Dodson, Mary E. Edwards, William D.
Connor Nolan, Jonathan T. Overpeck, Judy R. M. Allen, Patricia M. Anderson, Julio L. Betancourt, Heather A. Binney, Simon
DOI: 10.1126/science.aan5360
(6405), 920-923.361Science
, this issue p. 920Science
transformation in composition and structure.
(albeit more rapid) scenarios of warming. Without substantial mitigation efforts, terrestrial ecosystems are at risk of major
temperature changes of 4° to 7°C. They went on to estimate the extent of ecosystem changes under current similar
worldwide since the last glacial maximum 21,000 years ago. From this, they determined vegetation responses to
looked at documented vegetational and climatic changes at almost 600 siteset al.remains a challenge to predict. Nolan
Terrestrial ecosystems will be transformed by current anthropogenic change, but the extent of this change
Future predictions from paleoecology
This article cites 71 articles, 15 of which you can access for free
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... O clima muda no decorrer da história, de maneira mais ou menos cíclica, e altera o ambiente como um todo, sendo o principal fator de mudanças vegetacionais em grande escala (Webb, et al., 1998;Li, et al., 2018;Nolan, et al., 2018). Essas variações ocorrem por diversos fatores, como por exemplo a mudança do ângulo entre o eixo da Terra e o plano de sua órbita em torno do Sol ou a concentração de gases de efeito estufa na atmosfera, seja de forma natural ou antrópica (Tabor, et al., 2015;Walsh, et al., 2016;Marshall, et al., 2017). ...
... Climate change is driving alterations in moisture (Cook et al. 2014) and temperature (Hondula et al. 2015) patterns across a wide variety of landscapes. Moisture and temperature are key factors determining the net primary production of vegetation (Moritz et al. 2012), which influences the density and moisture content of flora (Nolan et al. 2018). ...
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Uncontrolled wildfires are occurring with increasing frequency across western North America due to a combination of wildfire suppression, climate change, impacts from mountain pine beetles (Dendroctonus ponderosae), alterations in range composition by nonnative grasses, and human population growth in fire‐prone landscapes. A poorly studied mechanism of wildland fire ignitions occurs when a bird perched on an overhead power line is electrocuted, its plumage ignites, and the burning bird falls into and ignites dry vegetation. Avian‐caused ignitions have been occasionally documented, but not spatially analyzed in the contiguous United States. We hypothesized that spatial analyses could demonstrate specific regions where ignitions from avian electrocutions occur most frequently. To test our hypothesis, we compared public reports of wildland fires ignited by bird electrocutions to Environmental Protection Agency ecoregions. We found reports of 44 wildland fires ignited by avian electrocutions in the contiguous U.S. from January 2014 to December 2018. The Mediterranean California ecoregion had the highest density of avian‐caused fires. It would be prudent for electric utilities in the Mediterranean California ecoregion in the U.S., and in fire‐prone landscapes globally, to develop fire mitigation plans that include modifying power poles to reduce risk of avian electrocutions and resulting wildfires. Wildland fires ignited by avian electrocutions are a risk multiplier for electric utilities, compounding semi‐predictable costs associated with wildlife take, power outages, and equipment damage with unpredictable costs associated with potentially catastrophic wildland fires. Electric utilities generally, particularly those in Mediterranean ecoregions, with cool, wet winters and hot, dry summers, should include in their fire mitigation plans, a focus on modifying power poles to reduce the risks of avian electrocutions and resulting wildfires.
... Climate change will increase global temperatures, as well as alter rainfall patterns and seasonality and the prevalence of extreme weather (IPCC, 2021), all of which are expected to increase the rate that new, 'novel', ecological communities appear into the future (Hobbs et al., 2009). Past periods of geological warming also caused ecological change (Nolan et al., 2018): in particular, the warming that drove glacial retreat and the end of the last Ice Age from 19,000 to 11,000 years before present (ybp) . During this period, average global temperatures rose by 4°C over the course of 8000 years (Jasechko et al., 2015). ...
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Anthropogenic disturbance and climate change can result in dramatic increases in the emergence of new, ecologically novel, communities of organisms. We used a standardised framework to detect local novel communities in 2135 pollen time series over the last 25,000 years. Eight thousand years of post‐glacial warming coincided with a threefold increase in local novel community emergence relative to glacial estimates. Novel communities emerged predominantly at high latitudes and were linked to global and local temperature change across multi‐millennial time intervals. In contrast, emergence of locally novel communities in the last 200 years, although already on par with glacial retreat estimates, occurred at midlatitudes and near high human population densities. Anthropogenic warming does not appear to be strongly associated with modern local novel communities, but may drive widespread emergence in the future, with legacy effects for millennia after warming abates.
... Records from before the instrumental era (Jouzel et al., 2007) show a similar amplitude of climatic oscillations as the current climate and the expected climate in the next decades. However, the main difference between the past millennia and the next century is the timescale over which climate change will occur and impact ecosystems and species (Nolan et al., 2018). Will today's fragmented populations of Atlas cedar have the capacity to survive under ongoing climate change? ...
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Assessing biodiversity loss and species extinction is necessary to warn society and raise awareness of the impacts of ongoing climate change. Prioritizing protected areas is the pragmatic and applicable management measure under the pressure of ongoing climate change and limited resources to conserve species at risk of extinction. We developed a novel conservation index (CI) to prioritize areas and populations of an endangered mountain tree species that need protection in the face of ongoing climate change, as conservation of all populations may not be realistic. This CI integrates (1) mountain topography to identify potential refugial areas with suitable microclimates, (2) genetic diversity to assess the adaptive capacity of local populations, and (3) hypothetical climate change in the species' range. We applied this CI to Atlas cedar, an endemic and threatened species whose populations are scattered throughout the Moroccan mountains. This index provided a scale for 33 populations studied and suggests that genetically diverse populations located in rugged areas where future local climate may overlap with their current climatic niche should receive a higher conservation priority. This index may also be applicable to other mountain species with scattered populations and is likely to be more accurate if more precise climate data are used at the microrefugia scale.
... It is expected that the boreal forest of these areas will not be immediately replaced by a temperate mixed forest where the average annual temperature exceeds the range of values typical of the taiga biome. Terrestrial vegetation compositional and structural change could occur during the 21st century where vegetation disturbance is accelerated or amplified by human activity, but equilibrium states may not be reached until the 22nd century or beyond 36 . Based on the assumption that during the future period (2070-2099) the vegetation will not be fully adapted to the new climatic conditions, and since the present Köppen-Geiger climate classification (on which we base our Tr, Ar, Te and Bo categories) closely corresponds to the different existent biomes 22 , we analyse only the projected changes in the specific fire-climate classification variables, maintaining the general division of Tropical, Arid, Temperate and Boreal regions as is in present climate conditions. ...
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Global warming is expected to alter wildfire potential and fire season severity, but the magnitude and location of change is still unclear. Here, we show that climate largely determines present fire-prone regions and their fire season. We categorize these regions according to the climatic characteristics of their fire season into four classes, within general Boreal, Temperate, Tropical and Arid climate zones. Based on climate model projections, we assess the modification of the fire-prone regions in extent and fire season length at the end of the 21st century. We find that due to global warming, the global area with frequent fire-prone conditions would increase by 29%, mostly in Boreal (+111%) and Temperate (+25%) zones, where there may also be a significant lengthening of the potential fire season. Our estimates of the global expansion of fire-prone areas highlight the large but uneven impact of a warming climate on Earth’s environment.
... Increased frequency and intensity of extreme episodes (e.g. heatwaves and severe droughts) may trigger greater limitation on plant growth and survival, leading to the abrupt losses in local species diversity, composition shifts and further declines in the carbon sink for terrestrial forest ecosystems (Ciais et al., 2005;Nolan et al., 2018;Trisos et al., 2020). Therefore, accurately understanding the dynamics of ecological recovery in waterstressed ecosystems is of great importance to conserve the local diversity and maintain ecosystem functions in a rapidly changing climate for coming decades. ...
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Increasing water deficits and severe droughts are expected to alter the dynamics of vegetation post-disturbance recovery by decreasing new recruitment and limiting growth in semi-arid Mediterranean ecosystems in future. However, which vegetation metrics will be shifted and how they respond over time are not clear, and the experimental evidence is still limited. Here we assessed the impacts of a long-term (20 years) experimental drought (−30% rainfall) on the pathways of vegetation metrics related to species richness, community composition and abundance dynamics for an early-successional Mediterranean shrubland. The results indicate that the pathways of vegetation metrics were differently affected by experimental drought. The abundance of Globularia alypum follows pathway 1 (altered mature state). Simpson diversity and abundance of Erica multiflora follow pathway 2 (delayed succession) while species richness, community abundance and shrub abundance follow pathway 3 (alternative stable state). There were no significances for the resilience to extremely dry years (the ratio between the performance after and before severe events) between control and drought treatment for all vegetation metric. But, their resilience for the metrics (except Simpson diversity) to extremely dry years in 2016–17 were significantly lower than that of 2001 and of 2006–07, possibly caused by the severe water deficits in 2016–17 at mature successional stage. Principal component analysis (PCA) shows that the first two principal components explained 72.3 % of the variance in vegetation metrics. The first axis was mainly related to the changes in community abundance, shrub abundance and species richness while the second axis was related to Simpson diversity and abundance of G. alypum and E. multiflora. Principal component scores along PC1 between control and drought treatment were significantly decreased by long-term experimental drought, but the scores along PC2 were not affected. Further research should focus on successional pathways in more water-deficit conditions in Mediterranean ecosystems and the consequences of changes in vegetation recovery pathways on ecosystem functions such as biomass accumulation and soil properties.
... In more explicitly Polanyian terms, projects of environmental protection via commodification might help to produce moderate levels of ecological embeddedness when, in fact, growing ecological crises demand much more rapid and far-reaching social and economic transformations (see e.g. Oreskes & Conway, 2014;Ciplet, Roberts & Khan, 2015;Dunlap & Brulle, 2015;Ostrom, 2016;Nolan et al., 2018). Carbon markets, in short, may help to depoliticize responses to climate change (Felli, 2015;Dempsey & Suarez, 2016). ...
Solar thermoelectric generator (STEG) is a relatively less efficient direct energy conversion device which converts input solar heat directly into electricity based on thermoelectric effects. A comprehensive model consisting the detailed electrical, thermodynamic and mechanical analysis of STEG is still missing in the literature. Thus, this paper presents a numerical model and analysis of a hybrid solar thermoelectric generator. The hybrid system is made up of a compound parabolic concentrator (CPC) attached to a thermoelectric module (TEM). A three-dimensional finite element model is developed and employed in analysing the hybrid system for varying concentrated solar irradiation and external load resistance. The optimum external load resistance, current, voltage and heat absorption rate required to maximise the electrical and thermodynamic performance of the device are obtained. The results in this study will provide useful information in the design of power generation systems.
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The evolution of disciplinary silos and increasingly narrow disciplinary boundaries have together resulted in one‐sided approaches to the study of land‐atmosphere interactions—a field that requires a bi‐directional approach to understand the complex feedbacks and interactions that occur. The integration of surface flux and atmospheric boundary layer measurements is therefore essential to advancing our understanding. The Land‐Atmosphere 2021 workshop (held virtually, June 10‐11, 2021) involved almost 300 participants from around the world and promoted cross‐discipline collaboration by way of talks from invited speakers, moderated discussions, breakout sessions, and a virtual poster session. The workshop focused on five main theme areas: “big picture” overview, instrumentation and remote sensing, modeling, water, and aerosols and clouds. In talks and breakout groups, there were frequent calls for more AmeriFlux sites to be instrumented for boundary layer height measurements, and for the development of some “super sites” where profiling instruments would be deployed. There was further agreement on the need for the standardization of various datasets. There was also a consensus that funding agencies need to be willing to support the sorts of large projects (including associated instrumentation) which can drive interdisciplinary work. Early‐career scientists, in particular, expressed enthusiasm for working across disciplinary boundaries but noted that there need to be more financial support and training opportunities so they would be better prepared for interdisciplinary work. Investment in these career development opportunities would enable today's cohort of early‐career scientists to advance the frontiers of interdisciplinary work over the next couple of decades.
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During the last deglaciation (∼19–11 ka before present), the global mean temperature increased by 3–8 K. The concurrent hydroclimate and land cover changes are not well constrained. Here, we use a pollen database to quantify global‐scale vegetation changes during this transitional period at orbital (∼10⁴ years) and millennial timescales (∼10³ years). We focus on the proportion of tree and shrub pollen, the arboreal pollen (AP) fraction. Temporal similarities over long distances are identified by a paleoclimate network approach. At the orbital scale, we find coherent AP variations in the low and mid‐latitudes which we attribute to the global climate forcing. While AP fractions predominantly increased through the deglaciation, we identify regions where AP fractions decreased. For millennial timescales, we do not observe spatially coherent similarity structures. We compare our results with networks computed from three deglacial climate simulations with the CCSM3, HadCM3, and LOVECLIM models. Networks based on simulated precipitation patterns reproduce the characteristics of the AP network. Sensitivity experiments with statistical emulators indicate that, indeed, precipitation variations explain the diagnosed patterns of vegetation change better than temperature and CO2 variations. Our findings support previous interpretations of deglacial forest evolution in the mid‐latitudes being the result of atmospheric circulation changes. The network analysis identifies differences in the vegetation‐climate‐CO2 relationship simulated by CCSM3 and HadCM3. We conclude that network analyses are a promising tool to benchmark transient climate simulations with dynamical vegetation changes. This may result in stronger constraints of future hydroclimate and land cover changes.
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Background: Anthropogenic climate change (ACC) will influence all aspects of plant biology over coming decades. Many changes in wild species have already been well-documented as a result of increased atmospheric CO2 concentrations, warming climate and changing precipitation regimes. A wealth of available data has allowed the use of meta-analyses to examine plant-climate interactions on more sophisticated levels than before. These analyses have revealed major differences in plant response among groups, e.g. with respect to functional traits, taxonomy, life-history and provenance. Interestingly, these meta-analyses have also exposed unexpected mismatches between theory, experimental, and observational studies. Scope: We reviewed the literature on species' responses to ACC, finding ∼42 % of 4000 species studied globally are plants (primarily terrestrial). We review impacts on phenology, distributions, ecophysiology, regeneration biology, plant-plant and plant-herbivore interactions, and the roles of plasticity and evolution. We focused on apparent deviations from expectation, and highlighted cases where more sophisticated analyses revealed that unexpected changes were, in fact, responses to ACC. Conclusions: We found that conventionally expected responses are generally well-understood, and that it is the aberrant responses that are now yielding greater insight into current and possible future impacts of ACC. We argue that inconclusive, unexpected, or counter-intuitive results should be embraced in order to understand apparent disconnects between theory, prediction, and observation. We highlight prime examples from the collection of papers in this Special Issue, as well as general literature. We found use of plant functional groupings/traits had mixed success, but that some underutilized approaches, such as Grime's C/S/R strategies, when incorporated, have improved understanding of observed responses. Despite inherent difficulties, we highlight the need for ecologists to conduct community-level experiments in systems that replicate multiple aspects of ACC. Specifically, we call for development of coordinating experiments across networks of field sites, both natural and man-made.
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Patterns, mechanisms, projections, and consequences of tree mortality and associated broad- scale forest die-off due to drought accompanied by warmer temperatures—‘‘hotter drought’’, an emerging characteristic of the Anthropocene—are the focus of rapidly expanding literature. Despite recent observational, experimental, and modeling studies suggesting increased vulnerability of trees to hotter drought and associated pests and pathogens, substantial debate remains among research, management and policy-making communities regarding future tree mortality risks. We summarize key mortality- relevant findings, differentiating between those implying lesser versus greater levels of vulnerability. Evidence suggesting lesser vulnerability includes forest benefits of elevated [CO2] and increased water-use efficiency; observed and modeled increases in forest growth and canopy greening; widespread increases in woody-plant biomass, density, and extent; compensatory physiological, morphological, and genetic mechanisms; dampening ecological feedbacks; and potential mitigation by forest management. In contrast, recent studies document more rapid mortality under hotter drought due to negative tree physiological responses and accelerated biotic attacks. Additional evidence suggesting greater vulnerability includes rising background mortality rates; projected increases in drought frequency, intensity, and duration; limitations of vegetation models such as inadequately represented mortality processes; warming feedbacks from die-off; and wildfire synergies. Grouping these findings we identify ten contrasting perspectives that shape the vulnerability debate but have not been discussed collectively. We also present a set of global vulnerability drivers that are known with high confidence: (1) droughts eventually occur everywhere; (2) warming produces hotter droughts; (3) atmospheric moisture demand increases nonlinearly with temperature during drought; (4) mortality can occur faster in hotter drought, consistent with fundamental physiology; (5) shorter droughts occur more frequently than longer droughts and can become lethal under warming, increasing the frequency of lethal drought nonlinearly; and (6) mortality happens rapidly relative to growth intervals needed for forest recovery. These high-confidence drivers, in concert with research supporting greater vulnerability perspectives, support an overall viewpoint of greater forest vulnerability globally. We surmise that mortality vulnerability is being discounted in part due to difficulties in predicting threshold responses to extreme climate events. Given the profound ecological and societal implications of underestimating global vulnerability to hotter drought, we highlight urgent challenges for research, management, and policy-making communities.
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Ongoing anthropogenic perturbations to the atmosphere and biosphere increase the risk of future abrupt changes in the climate system and generate concern about the ability of natural ecosystems to respond to rapid climate change. Study of past climatic events and biotic responses can inform us about potential future change. Qualitatively fast local responses of plant taxa to abrupt late glacial climate oscillations have been reported from individual records and attributed to short migration distances in areas of high topographic relief. By using quantitative time-series analyses, we show that vegetation responses to late glacial climate change around the North Atlantic were rapid and widespread and occurred in areas of differing relief. Cross-correlation analysis of 11 high-resolution lacustrine records in eastern North America and Europe indicates vegetation-response times consistently of <200 yr and often <100 yr, despite regional differences in physiography and species composition. Vegetation lags of <200 yr confirm theoretical predictions, and the apparently tight coupling between vegetation and atmosphere suggests that recent climatic trends may already have begun to affect plant population abundances and distributions.
Impacts of global climate change on terrestrial ecosystems are imperfectly constrained by ecosystem models and direct observations. Pervasive ecosystem transformations occurred in response to warming and associated climatic changes during the last glacial-to-interglacial transition, which was comparable in magnitude to warming projected for the next century under high-emission scenarios.We reviewed 594 published paleoecological records to examine compositional and structural changes in terrestrial vegetation since the last glacial period and to project the magnitudes of ecosystem transformations under alternative future emission scenarios. Our results indicate that terrestrial ecosystems are highly sensitive to temperature change and suggest that, without major reductions in greenhouse gas emissions to the atmosphere, terrestrial ecosystems worldwide are at risk of major transformation, with accompanying disruption of ecosystem services and impacts on biodiversity. Authors: Connor Nolan, Jonathan T. Overpeck, Judy R. M. Allen, Patricia M. Anderson, Julio L. Betancourt, Heather A. Binney, Simon Brewer, Mark B. Bush, Brian M. Chase, Rachid Cheddadi, Morteza Djamali, John Dodson, Mary E. Edwards, William D. Gosling, Simon Haberle, Sara C. Hotchkiss, Brian Huntley, Sarah J. Ivory, A. Peter Kershaw, Soo-Hyun Kim, Claudio Latorre, Michelle Leydet, Anne-Marie Lézine, Kam-Biu Liu, Yao Liu, A. V. Lozhkin, Matt S. McGlone, Robert A. Marchant, Arata Momohara, Patricio I. Moreno, Stefanie Müller, Bette L. Otto-Bliesner, Caiming Shen, Janelle Stevenson, Hikaru Takahara, Pavel E. Tarasov, John Tipton, Annie Vincens, Chengyu Weng, Qinghai Xu, Zhuo Zheng, Stephen T. Jackson
Ecological memory is central to how ecosystems respond to disturbance and is maintained by two types of legacies – information and material. Species life-history traits represent an adaptive response to disturbance and are an information legacy; in contrast, the abiotic and biotic structures (such as seeds or nutrients) produced by single disturbance events are material legacies. Disturbance characteristics that support or maintain these legacies enhance ecological resilience and maintain a “safe operating space” for ecosystem recovery. However, legacies can be lost or diminished as disturbance regimes and environmental conditions change, generating a “resilience debt” that manifests only after the system is disturbed. Strong effects of ecological memory on post-disturbance dynamics imply that contingencies (effects that cannot be predicted with certainty) of individual disturbances, interactions among disturbances, and climate variability combine to affect ecosystem resilience. We illustrate these concepts and introduce a novel ecosystem resilience framework with examples of forest disturbances, primarily from North America. Identifying legacies that support resilience in a particular ecosystem can help scientists and resource managers anticipate when disturbances may trigger abrupt shifts in forest ecosystems, and when forests are likely to be resilient.
The 2012-2015 drought has left California with severely reduced snowpack, soil moisture, ground water, and reservoir stocks, but the impact of this estimated millennial-scale event on forest health is unknown. We used airborne laser-guided spectroscopy and satellite-based models to assess losses in canopy water content of California's forests between 2011 and 2015. Approximately 10.6 million ha of forest containing up to 888 million large trees experienced measurable loss in canopy water content during this drought period. Severe canopy water losses of greater than 30% occurred over 1 million ha, affecting up to 58 million large trees. Our measurements exclude forests affected by fire between 2011 and 2015. If drought conditions continue or reoccur, even with temporary reprieves such as El Niño, we predict substantial future forest change.
Projections of ecosystem and biodiversity change for Africa under climate change diverge widely. More than other continents, Africa has disturbance-driven ecosystems that diversified under low Neogene CO2 levels, in which flammable fire-dependent C4 grasses suppress trees, and mega-herbivore action alters vegetation significantly. An important consequence is metastability of vegetation state, with rapid vegetation switches occurring, some driven by anthropogenic CO2-stimulated release of trees from disturbance control. These have conflicting implications for biodiversity and carbon sequestration relevant for policymakers and land managers. Biodiversity and ecosystem change projections need to account for both disturbance control and direct climate control of vegetation structure and function.
Although disturbances such as fire and native insects can contribute to natural dynamics of forest health, exceptional droughts, directly and in combination with other disturbance factors, are pushing some temperate forests beyond thresholds of sustainability. Interactions from increasing temperatures, drought, native insects and pathogens, and uncharacteristically severe wildfire are resulting in forest mortality beyond the levels of 20th-century experience. Additional anthropogenic stressors, such as atmospheric pollution and invasive species, further weaken trees in some regions. Although continuing climate change will likely drive many areas of temperate forest toward large-scale transformations, management actions can help ease transitions and minimize losses of socially valued ecosystem services. Copyright © 2015, American Association for the Advancement of Science.
Past Assessments The topics assessed in this chapter were last assessed by the IPCC in 2007, principally in WGII AR4 Chapters 3 (Kundzewicz et al., 2007) and 4 (Fischlin et al., 2007), but also in WGII AR4 Sections 1.3.4 and 1.3.5 (Rosenzweig et al., 2007). The WGII AR4 SPM stated "Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases," though they noted that documentation of observed changes in tropical regions and the Southern Hemisphere was sparse (Rosenzweig et al., 2007). Fischlin et al. (2007) found that 20 to 30% of the plant and animal species that had been assessed to that time were considered to be at increased risk of extinction if the global average temperature increase exceeds 2°C to 3°C above the preindustrial level with medium confidence, and that substantial changes in structure and functioning of terrestrial, marine, and other aquatic ecosystems are very likely under that degree of warming and associated atmospheric CO2 concentration. No time scale was associated with these findings. The carbon stocks in terrestrial ecosystems were considered to be at high risk from climate change and land use change. The report warned that the capacity of ecosystems to adapt naturally to the combined effect of climate change and other stressors is likely to be exceeded if greenhouse gas (GHG) emission continued at or above the then-current rate. 4.2. A Dynamic and Inclusive View of Ecosystems There are three aspects of the contemporary scientific view of ecosystems that are important to know for policy purposes. First, ecosystems usually have imprecise and variable boundaries. They span a wide range of spatial scales, nested within one another, from the whole biosphere, down through its major ecosystem types (biomes), to local and possibly short-lived associations of organisms. Second, the human influence on ecosystems is globally pervasive. Humans are regarded as an integral, rather than separate, part of social-ecological systems (Gunderson and Holling, 2001; Berkes et al., 2003).