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Integrating climate, ecophysiology, and forest cover to estimate the vulnerability of sloths to climate change
Abstract
Global change imposes multiple challenges on species and, thus, a reliable prediction of current and future vulnerability of species must consider multiple stressors and intrinsic traits of species. Climate, physiology, and forest cover, for example, are required to evaluate threat to thermolabile forest-dependent species, such as sloths (Bradypus spp.; Mammalia: Xenarthra). Here, we estimated future changes in the distribution of three sloth species using a metabolic-hybrid model focused on climate (climatic only, i.e., CO approach) and adding forest cover constraints to distribution of species (climate plus land cover, i.e., CL approach). We used an innovative method to generate estimates of physiological parameters for endotherms, validated with field data. The CF approach predicted a future net expansion of distribution of B. torquatus and B. variegatus, and a future net contraction of distribution of B. tridactylus. The inclusion of forest cover constraints, however, reversed the predictions for B. torquatus, with a predicted net distribution contraction. It also reduced expansion of B. variegatus, although still showing a large net expansion. Thus, B. variegatus is not predicted to be threatened in the future; B. tridactylus emerges as the species most vulnerable to climate change, but with no considerable forest losses, while B. torquatus shows the opposite pattern. Our study highlights the importance of incorporating multiple stressors in predictive models in general. To increase resilience of species to climate change, it is key to control deforestation in the Amazon for B. tridactylus, and to promote reforestation in the Atlantic Forest for B. torquatus.
... Although the effects of ambient temperature and sun condition (sunny, cloudy, or rainy) on sloths' behaviour have been previously studied (Britton & Atkinson, 1938;Cliffe et al., 2018;Giné et al., 2015;Montgomery & Sunquist, 1978), the joint effect of these variables has never been statistically evaluated in free-ranging sloths. As the three-toed sloths are potentially sensitive to fluctuations in temperature and sun conditions, the maned sloth may be particularly vulnerable in the face of global climate changes and landscape changes occurring in the Atlantic Forest (Santos et al., 2019Tourinho et al., 2022). Particularly, behavioural changes driven by climate change (activity levels, forest strata selection and frequency of postures adopted) might make them more detectable and vulnerable to human pressures, such as hunting. ...
... In this scenario, sloths may be exposed to conditions in which thermoregulatory behaviours will no longer be effective to avoid overheating or even maintain a positive energy and water balance, an issue to be investigated. This is even more worrying when we consider the recent revision of B. torquatus taxonomy and the projections of future suitable areas for the species, which indicate more restrict distribution range and no future expansion in their habitat, respectively (Miranda et al., 2022;Tourinho et al., 2022). ...
... It is possible that a warmer and drier future in the already warm northern Atlantic Forest may bring some changes in maned sloths' behaviours and challenges to this species that rely on thermoregulatory behaviours to control body temperature (Kearney et al., 2009). Maned sloths are vulnerable to habitat loss and a myriad of anthropogenic pressures (Chiarello & Moraes-Barros, 2014;Santos et al., 2019;Tourinho et al., 2022), and such future conditions could be an additional threatening factor, which may affect their physiology, metabolism and behaviour (Cliffe et al., 2018;Deutsch et al., 2008;Kearney et al., 2009). We offer information that can be combined with climate data to spatially predict the future impacts of climate change on its distribution and behaviour. ...
Changes in ambient temperature and solar radiation may affect sloths' metabolic rate and body temperature, with consequent changes in activities, postures and microhabitat selection. Although the separate effect of temperature and solar radiation on sloth's behaviour have been previously studied, the combined effect of these climatic factors on behavioural aspects of sloths has never been systematically evaluated in field conditions. Here we evaluated the influence of hourly ambient temperature variation on maned sloth ( Bradypus torquatus ) activities, postures and tree crown positions, under sunny and cloudy conditions; and tested if any of the animal posture and position increase their exposure to human detection. We performed 350 h of visual observation on eight maned sloths, equipped with radio‐backpacks, in northern Bahia, Brazil, recording their activities, and their resting postures and positions on tree crowns. We also recorded the time taken to visualize the sloths on 58 days to analyse if sloths' detection is affected by posture and position. Higher ambient temperature, within a range of 21–33°C, increased the sloths' activity levels in cloudy conditions but reduced their activity in sunny conditions. Increasing ambient temperature also reduced the frequency of huddled posture and increased the frequency of extended posture and permanence in the inner tree crown. Lastly, the postures and positions did not influence sloths' detectability. Thus, the direction of the temperature–activity relationship depends on climatic conditions (sunny/cloudy), and individuals rely on resting postures and positions to thermoregulate. The warmer and drier future climate, expected to occur in the northern Atlantic Forest, may impose change in the diurnal activity levels and postural pattern for this threatened species, leading maned sloths to reduce its activity on sunny and warmer days and adopting an extended posture.
... Ecological niche modeling is a great tool to predict climate change impacts on biodiversity, but it usually does not include important determinants of vulnerability to climate change, such as species' ecological interactions, dispersal ability, physiology, and adaptive potential (Tourinho and Vale, 2023). Recently, some of these responses have been assessed in South American studies, forecasting shifts in species distribution attributed to climate and land-cover changes, with most species predicted to contract their distributions in the future (e.g., Diniz-Filho et al., 2019;Tourinho et al., 2021Tourinho et al., , 2022Tourinho et al., , 2023Portela et al., 2023). The observed impact on plant species in the South American Monsoon region is also expected to worsen in a warmer climate. ...
... Both modelling approaches relied on climatic conditions during the activity period only, which did not reflect possible critical limits associated with winter conditions. Including independent data allows to clarify the extent of the species' distribution (Buckley et al., 2023;Tourinho et al., 2022), such as permafrost, for the northern limits of these two species. Overall, we are confident that PMV modelling offers here a more robust approach to define current and projected past distributions. ...
Aim
Ecological niche‐based models (ENM) frequently rely on bioclimatic variables (BioV) to reconstruct biogeographic scenarios for species evolution, ignoring mechanistic relations. We tested if climatic predictors relevant to species hydric and thermal physiology better proximate distribution patterns and support location of Pleistocene refugia derived from phylogeographic studies.
Location
The Western Palaearctic.
Taxon
Vipera berus and Zootoca vivipara , two cold‐adapted species.
Methods
We used two sets of variables, that is physiologically meaningful climatic variables (PMV) and BioV, in a multi‐algorithm ENM approach, to compare their ability to predict current and Last Glacial Maximum (LGM) species ranges. We estimated current and LGM permafrost extent to address spatially the cold hardiness dissimilarity between both species.
Results
PMV explained more accurately the current distribution of these two cold‐adapted species and identified the importance of summer temperature and solar radiation that constrain activity in cold habitats. PMV also provide a better insight than BioV predictors on LGM distribution. By including notably, the permafrost extent, PMV‐based models gave parsimonious putative arrangement and validity of refugia for each clade and subclade in accordance with phylogeographic data. Northern refugia were also identified from 48 to 52° N for V. berus and from 50 to 54° N for Z. vivipara .
Main Conclusions
Our hybrid approach based on PMV generated more realistic predictions for both current (biogeographical validation) and past distributions (phylogeographic validation). By combining constraints during the activity period (summer climatic niche) and those inherent to the wintering period (freeze tolerance), we managed to identify glacial refuges in agreement with phylogeographic hypotheses concerning post‐glacial routes and colonization scenarios.
... Considering that a reliable prediction of current and future vulnerability of species should include multiple stressors and biological interactions (Araújo & Luoto, 2007;Tourinho, Sinervo, et al., 2022;Urban et al., 2016), the objective of this study was to evaluate whether the overlap of the distribution of the E. edulis with its seed dispersers and seed predators would change under future climate change, discussing possible consequences for the species' viability in the future. ...
Ongoing climate change has caused well‐documented displacements of species' geographic distribution to newly climatically suitable areas. Ecological niche models (ENM) are widely used to project such climate‐induced changes but typically ignore species' interspecific interactions that might facilitate or prevent its establishment in new areas. Here, we projected the change in the distribution of Juçara Palm ( Euterpe edulis Mart., Arecaceae), a neotropical threatened palm, taking into consideration its ecological interactions. We run ENMs of E. edulis , plus its known seed dispersers (15 bird species) and predators (19 birds and mammals) under current and future climatic conditions. Additionally, for E. edulis , we removed deforested areas from the model. When considering only climate, climate change has a positive impact on E. edulis , with a predicted westward expansion and a modest southward contraction, with a 26% net gain in distribution by 2060. When removing deforested areas, however, climate change harms E. edulis , with a 66% predicted net distribution loss. Within the palm's distribution in this more realistic model, there is also a predicted reduction in the richness of its dispersers and predators. We conclude that the possible benefits of climate change to E. edulis ' distribution are overshadowed by widespread habitat loss, and that global change is likely to disrupt some of its ecological interactions. The outcome of the interplay between the negative impact of the loss of dispersers, and the benefit of the loss of predators, is unclear, but the large contraction of E. edulis ' range predicted here foresees a dim future for the species.
Abstract in Portuguese is available with online material.
... The floristic composition and diversity vary greatly along the species distribution range, as it encompasses different biogeographical sub-regions within the Atlantic Forest biome (da Silva and Casteleti 2003) in addition to more local variation such as, Restinga forests over sandy soils on the coast, low land moist forest over latisols and podizols, and montane forests above 500 m of elevation (Thomas 2003). A better understanding of the feeding ecology of the maned sloth can provide support for forest restoration programs aiming at their conservation, particularly recommended in Rio de Janeiro and northern BA (Souto 2022;Tourinho et al. 2022), as well as, for ex situ management (ICMBio 2018). The survival, rehabilitation, and reproduction of maned sloths in captivity have been a challenge, with high mortality of animals by anorexia and decumbency due to inadequate feeding management (Arenales et al. 2020). ...
Individual diet specialization is commonly found in generalist species but has been little studied in folivore mammals. Empirical evidence shows that the diversity of food resources in the habitat affects the degree of this specialization, by influencing among-individual diet variation (diet similarity) and individual niche breadth (diet diversity). We aim to evaluate the diet composition and selection of maned sloths (Bradypus torquatus, Illiger 1811) in two distinct ecological contexts; test whether the diet similarity between individuals and populations is explained by changes in the local floristic compositions and/or by a differentiated selection of tree species, and evaluate the effect of the local tree diversity on the diet diversity and similarity across individuals. We monitored 13 individuals in northern Bahia and Rio de Janeiro and accessed the tree species diversity and availability within each home range. We identified 67 tree species consumed, most of which were consumed in higher proportion than their availability in the home ranges, indicating high selectivity by the individuals. Diet similarity decreased with greater differences in the local floristic composition and higher tree diversity, but was also influenced by individual selection. Together, our results evidence that the maned sloth is specialist and selective at the individual level, and the lower tree diversity reduces individual diet specialization, revealing tree species that are commonly preferred at the population level under such condition. Our results can be directly applied to feeding protocols of captive populations, and ecological restoration initiatives focusing on the conservation of this threatened species.
Background: Maned sloths are docile mammals endemic to the Brazilian Atlantic Forest, threatened with extinction due to the degradation of their habitat. Injury involving limbs is common when animals enter the urban environment. However, information regarding anesthesia in sloths is still scarce. This case is intended to report the anesthetic management of a maned three-toed sloth adult female undergoing amputation of the forelimb. Case: A female maned three-toed sloth weighing 4.2 kg with a history of burns to the thoracic forearm caused by electric shock was admitted by the University Veterinary Hospital. Ketamine (6 mg/kg - IM) and midazolam (0.2 mg/kg - IM) were administered as premedication, and after 10 min, tramadol (2 mg/kg - IV) was used. After detecting good general condition, the animal was referred to the surgical center for forearm amputation. Anesthetic induction was performed using isoflurane 2.5% (FiO2 = 1.0) via a mask, followed by intubation and maintenance using the same drug (1.5%). Next, the vertebrae C7 to C10 and T1 to T2 were identified, corresponding to the 7th, 8th, 9th, and 10th cervical medullary segments and the 1st and 2nd thoracic medullary segments, corresponding to the respective related spinal nerves, which give rise to the brachial plexus in the species. The vertebral foramen was accessed using a hypodermic needle inserted cranially and caudally to the transverse processes of C7, C8, C9, and C10 at a distance of 1 cm, laterally to the right of the animal's dorsal midline at a 45º angle to the vertebral column. The 1st rib palpated dorsally allowed T1 and T2 to be located, and the needle was inserted according to the delimitations already described. The brachial plexus was blocked with 0.5 mL of lidocaine solution (1.5%) into each intervertebral foramen. After 10 min, the animal underwent thoracic limb amputation. Heart rate (HR), respiratory rate (f), end-tidal carbon dioxide (EtCO2), peripheral oxyhemoglobin saturation (SpO2), and rectal temperature (RT) were registered using a multiparametric monitor. The parameters recorded throughout the 50-min interval of the surgical procedure remained within the regular pattern of species. End-tidal isoflurane (EtISO) registered were 1.03 ± 0.19 mmHg. No movements were observed responding to pain stimuli, and the animal exhibited smooth recovery in 28 min. Discussion: Although limb trauma is a frequently reported condition, this study is a pioneer in the approach of using paravertebral brachial plexus block as part of the anesthetic protocol in sloths. Initially, a ketamine-midazolam combination was used to immobilize the animal for handling and preoperative clinical assessments. This combination of dissociative anesthetics with muscle relaxants has been widely used in anteaters and sloths, with physiological stability and smooth recovery reported. As thoracic limb amputation is a painful procedure, tramadol was used as an analgesic. Isoflurane was used for anesthesia maintenance, as reported in other studies with sloths. Brachial block using cervicothoracic access to the nerve roots that give rise to the brachial plexus was considered easy to perform. Lidocaine with vasoconstrictor was chosen based on the duration of the surgical procedure. Maintaining the sloth in a mild anesthetic plane associated with low isoflurane intraoperative requirement demonstrated the analgesic effectiveness of the locoregional block. The proposed anesthetic protocol was effective and safe, evidenced by stable physiological variables, no pain-related movements during surgery, and gentle animal awakening. Keywords: xenarthra anesthesia, ketamine, isoflurane, locoregional anesthesia.
Climate change is expected to cause irreversible changes to biodiversity, but predicting those risks remains uncertain. I synthesized 485 studies and more than 5 million projections to produce a quantitative global assessment of climate change extinctions. With increased certainty, this meta-analysis suggests that extinctions will accelerate rapidly if global temperatures exceed 1.5°C. The highest-emission scenario would threaten approximately one-third of species, globally. Amphibians; species from mountain, island, and freshwater ecosystems; and species inhabiting South America, Australia, and New Zealand face the greatest threats. In line with predictions, climate change has contributed to an increasing proportion of observed global extinctions since 1970. Besides limiting greenhouse gases, pinpointing which species to protect first will be critical for preserving biodiversity until anthropogenic climate change is halted and reversed.
Although climate change is predicted to have a substantial effect on the energetic requirements of organisms, the longer-term implications are often unclear. Sloths are limited by the rate at which they can acquire energy and are unable to regulate core body temperature (T b ) to the extent seen in most mammals. Therefore, the metabolic impacts of climate change on sloths are expected to be profound. Here we use indirect calorimetry to measure the oxygen consumption (VO 2 ) and T b of highland and lowland two-fingered sloths ( Choloepus hoffmanni) when exposed to a range of different ambient temperatures (T a ) (18 °C –34 °C), and additionally record changes in T b and posture over several days in response to natural fluctuations in T a . We use the resultant data to predict the impact of future climate change on the metabolic rate and T b of the different sloth populations. The metabolic responses of sloths originating from the two sites differed at high T a ’s, with lowland sloths invoking metabolic depression as temperatures rose above their apparent ‘thermally-active zone’ (TAZ), whereas highland sloths showed increased RMR. Based on climate change estimates for the year 2100, we predict that high-altitude sloths are likely to experience a substantial increase in metabolic rate which, due to their intrinsic energy processing limitations and restricted geographical plasticity, may make their survival untenable in a warming climate.
Land-use land-cover (LULC) data are important predictors of species occurrence and biodiversity threat. Although there are LULC datasets available for ecologists under current conditions, there is a lack of such data under historical and future climatic conditions. This hinders, for example, projecting niche and distribution models under global change scenarios at different times. The Land Use Harmonization Project (LUH2) is a global terrestrial dataset at 0.25o spatial resolution that provides LULC data from 850 to 2300 for 12 LULC state classes. The dataset, however, is compressed in a file format (NetCDF) that is incompatible with most ecological analysis and intractable for most ecologists. Here we selected and transformed the LUH2 data in order to make it more useful for ecological studies. We provide LULC for every year from 850 to 2100, with data from 2015 on provided under two Shared Socioeconomic Pathways (SSP2 and SSP5). We provide two types of file for each year: separate files with continuous values for each of the 12 LULC state classes, and a single categorical file with all state classes combined. To create the categorical layer, we assigned the state with the highest value in a given pixel among the 12 continuous data. The final dataset provides LULC data for 1251 years that will be of interest for macroecology, ecological niche modeling, global change analysis, and other applications in ecology and conservation. We also provide a description of LUH2 prediction of future LULC change through time.
Amazonia hosts the Earth’s largest tropical forests and has been shown to be an important carbon sink over recent decades1,2,3. This carbon sink seems to be in decline, however, as a result of factors such as deforestation and climate change1,2,3. Here we investigate Amazonia’s carbon budget and the main drivers responsible for its change into a carbon source. We performed 590 aircraft vertical profiling measurements of lower-tropospheric concentrations of carbon dioxide and carbon monoxide at four sites in Amazonia from 2010 to 2018⁴. We find that total carbon emissions are greater in eastern Amazonia than in the western part, mostly as a result of spatial differences in carbon-monoxide-derived fire emissions. Southeastern Amazonia, in particular, acts as a net carbon source (total carbon flux minus fire emissions) to the atmosphere. Over the past 40 years, eastern Amazonia has been subjected to more deforestation, warming and moisture stress than the western part, especially during the dry season, with the southeast experiencing the strongest trends5,6,7,8,9. We explore the effect of climate change and deforestation trends on carbon emissions at our study sites, and find that the intensification of the dry season and an increase in deforestation seem to promote ecosystem stress, increase in fire occurrence, and higher carbon emissions in the eastern Amazon. This is in line with recent studies that indicate an increase in tree mortality and a reduction in photosynthesis as a result of climatic changes across Amazonia1,10.
Understanding the dynamics of native forest loss and gain is critical for biodiversity conservation and ecosystem services, especially in regions experiencing intense forest transformations. We quantified native forest cover dynamics on an annual basis from 1990 to 2017 in Brazil’s Atlantic Forest. Despite the relative stability of native forest cover during this period (~28 Mha), the ongoing loss of older native forests, mostly on flatter terrains, have been hidden by the increasing gain of younger native forest cover, mostly on marginal lands for mechanized agriculture. Changes in native forest cover and its spatial distribution increased forest isolation in 36.4% of the landscapes. The clearance of older forests associated with the recut of 27% of younger forests has resulted in a progressive rejuvenation of the native forest cover. We highlight the need to include native forest spatiotemporal dynamics into restoration programs to better estimate their expected benefits and unexpected problems.
This book provides a first synthetic view of an emerging area of ecology and biogeography, linking individual- and population-level processes to geographic distributions and biodiversity patterns. Problems in evolutionary ecology, macroecology, and biogeography are illuminated by this integrative view. The book focuses on correlative approaches known as ecological niche modeling, species distribution modeling, or habitat suitability modeling, which use associations between known occurrences of species and environmental variables to identify environmental conditions under which populations can be maintained. The spatial distribution of environments suitable for the species can then be estimated: a potential distribution for the species. This approach has broad applicability to ecology, evolution, biogeography, and conservation biology, as well as to understanding the geographic potential of invasive species and infectious diseases, and the biological implications of climate change. The book lays out conceptual foundations and general principles for understanding and interpreting species distributions with respect to geography and environment. Focus is on development of niche models. While serving as a guide for students and researchers, the book also provides a theoretical framework to support future progress in the field.
Environmental temperatures influence ectotherms’ physiology and capacity to perform activities necessary for survival and reproduction. Time available to perform those activities is determined by thermal tolerances and environmental temperatures. Estimates of activity time might enhance our ability to predict suitable areas for species’ persistence in face of climate warming, compared to the exclusive use of environmental temperatures, without considering thermal tolerances. We compare the ability of environmental temperatures and estimates of activity time to predict the geographic distribution of a tropical lizard, Tropidurus torquatus. We compared 105 estimates of activity time, resulting from the combination of four methodological decisions: 1) how to estimate daily environmental temperature variation (modeling a sinusoid wave ranging from monthly minimum to maximum temperature, extrapolating from operative temperatures measured in field or using biophysical projections of microclimate)? 2) In which temperature range are animals considered active? 3) Should these ranges be determined from body temperatures obtained in laboratory or in field? And 4) should thermoregulation simulations be included in estimations? We show that models using estimates of activity time made with the sinusoid and biophysical methods had higher predictive accuracy than those using environmental temperatures alone. Estimates made using the central 90% of temperatures measured in a thermal gradient as the temperature range for activity also ranked higher than environmental temperatures. Thermoregulation simulations did not improve model accuracy. Precipitation ranked higher than thermally related predictors. Activity time adds important information to distribution modeling and should be considered as a predictor in studies of the distribution of ectotherms. The distribution of T. torquatus is restricted by precipitation and by the effect of lower temperatures on their time of activty and climate warming could lead to range expansion. We provide an R package ‘Mapinguari’ with tools to generate spatial predictors based on the processes described herein.
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The International Union for Conservation of Nature (IUCN) Red List of Threatened Species includes assessment of extinction risk for 98 512 species, plus documentation of their range, habitat, elevation, and other factors. These range, habitat and elevation data can be matched with terrestrial land cover and elevation datasets to map the species' area of habitat (AOH; also known as extent of suitable habitat; ESH). This differs from the two spatial metrics used for assessing extinction risk in the IUCN Red List criteria: extent of occurrence (EOO) and area of occupancy (AOO). AOH can guide conservation, for example, through targeting areas for field surveys, assessing proportions of species' habitat within protected areas, and monitoring habitat loss and fragmentation. We recommend that IUCN Red List assessments document AOH wherever practical.
Forests are one of the most cost-effective ways to sequester carbon today. Here, I estimate the world’s land share under forests required to prevent dangerous climate change. For this, I combine newest longitudinal data of FLUXNET on forests’ net ecosystem exchange of carbon (NEE) from 78 forest sites (N = 607) with countries’ mean temperature and forest area. This straightforward approach indicates that the world’s forests sequester 8.3 GtCO2year⁻¹. For the 2 °C climate target, the current forest land share has to be doubled to 60.0% to sequester an additional 7.8 GtCO2year⁻¹, which demands less red meat consumption. This afforestation/reforestation (AR) challenge is achievable, as the estimated global biophysical potential of AR is 8.0 GtCO2year⁻¹ safeguarding food supply for 10 billion people. Climate-responsible countries have the highest AR potential. For effective climate policies, knowledge on the major drivers of forest area is crucial. Enhancing information here, I analyze forest land share data of 98 countries from 1990 to 2015 applying causal inference (N = 2494). The results highlight that population growth, industrialization, and increasing temperature reduce forest land share, while more protected forest and economic growth generally increase it. In all, this study confirms the potential of AR for climate change mitigation with a straightforward approach based on the direct measurement of NEE. This might provide a more valid picture given the shortcomings of indirect carbon stock-based inventories. The analysis identifies future regional hotspots for the AR potential and informs the need for fast and forceful action to prevent dangerous climate change.
Achieving ambitious global restoration commitments is a huge challenge. The Atlantic Forest Restoration Pact, created in 2009 as a movement to restore 15 Mha of degraded/deforested lands by 2050, pledged 1 Mha towards the 2020 Bonn Challenge. We documented the restoration of an estimated 673,510–740,555 ha of native forests from 2011 to 2015 in the Atlantic Forest, and expect that a total of 1.35–1.48 Mha will be under recovery by 2020. The Pact is one of the first Brazilian restoration initiatives to monitor an international restoration commitment and to demonstrate that ambitious targets can be reached. Part of this success in large-scale restoration is related to three main Pact activities: (i) development of restoration governance, communication and articulation; (ii) promotion of strategies to influence public policies; and (iii) establishment of restoration monitoring systems. The experience and lessons learned by the Pact could inspire and inform other restoration initiatives worldwide.
Insights into the causal mechanisms that limit species distributions are likely to improve our ability to anticipate species range shifts in response to climate change. For species with complex life‐histories, a mechanistic understanding of how climate affects different lifecycle stages may be crucial for making accurate forecasts. Here we use mechanistic niche modelling (NicheMapR) to derive ‘proximate’ (mechanistic) variables for tadpole, juvenile, and adult Rana temporaria. We modelled the hydroperiod, and maximum and minimum temperatures of shallow (30 cm) ponds, as well as activity windows for juveniles and adults. We then used those (‘proximate’) variables in correlative ecological niche models (Maxent) to assess their role in limiting the species’ current distribution, and to investigate the potential effects of climate change on R. temporaria across Europe. We further compared results with a model based on commonly used macroclimatic (‘distal’) layers (i.e. bioclimatic layers from WorldClim). Maximum temperature of the warmest month (a macroclimatic variable) and maximum pond temperatures (a mechanistic variable) were the most important range‐limiting factors, and maximum temperature thresholds were consistent with the observed upper thermal limit of R. temporaria tadpoles. We found that range shift forecasts in central Europe are far more pessimistic when using distal macroclimatic variables, compared to projections based on proximate mechanistic variables. However, both approaches predicted extensive decreases in climatic suitability in southern Europe, which harbors a significant fraction of the species’ genetic diversity. We show how mechanistic modelling provides ways to depict gridded layers that directly reflect the microenvironments experienced by organisms at continental scales, and to reconstruct those predictors without extrapolation under novel future conditions. Furthermore, incorporating those predictors in correlative ecological niche models can help shed light on range‐limiting processes, and can have substantial impacts on predictions of climate‐induced range shifts. This article is protected by copyright. All rights reserved.
Changing forest cover is a key driver of local climate change worldwide, as it affects both albedo and evapotranspiration (ET). Deforestation and forestation are predicted to have opposing influences on surface albedo and ET rates, and thus impact local surface temperatures differently. Relationships between forest change, albedo, ET, and local temperatures may further vary regionally, as the strengths of warming by albedo effects and cooling by ET effects vary with latitude. Despite these important relationships, the magnitude of forest cover effects on local surface temperature across the globe remains unclear. Using recently-released global forest change data, we first show that forestation and deforestation have pervasive and opposite effects on LST, ET and albedo worldwide. Deforestation from 2000 to 2010 caused consistent warming of 0.38 ± 0.02 (mean ± SE) and 0.16 ± 0.01°C in tropical and temperate regions respectively, while forestation caused cooling in those regions of -0.18 ± 0.02 and -0.19 ± 0.02°C. Tropical forests were particularly sensitive to the climate effects of forest change, with forest cover losses of ~50% associated with increased LST of 1.08 ± 0.25°C, whereas similar forest cover gains decreased LST by -1.11 ± 0.26°C. Secondly, based on a new structural equation model, we show that these changes on LST were largely mediated by changes in albedo and ET. Finally, based on this model, we show that predicted forest changes in Brazil associated with a business-as-usual land use scenario through 2050 may increase LST up to 1.45°C. Our results contribute to a better understanding of the mechanistic inter-relationships between forest change and changes in albedo, ET and LST, and provide additional evidence that forestation has the potential to reverse deforestation impacts on local climate, especially in tropical and temperate regions.
Aim
The idea of combining predictions from different models into an ensemble has gained considerable popularity in species distribution modelling, partly due to free and comprehensive software such as the R package BIOMOD. However, despite proliferation of ensemble models, we lack oversight of how and where they are used for modelling distributions, and how well they perform. Here, we present such an overview.
Location
Global.
Methods
Since BIOMOD is freely available and widely used by ensemble species distribution modellers, we focused on articles that apply BIOMOD, filtering the initial 852 papers identified in our structured literature search to a relevant final subset of 224 eligible peer‐reviewed journal articles.
Results
BIOMOD‐based ensembles are used across many taxa and locations, with terrestrial plants being the most represented group of species (n = 72) and Europe being the most represented continent (n = 106). These studies often focus on forecasting distributions in the future (n = 109), and commonly use presence‐only species data (n = 139) and climatic environmental predictors (n = 219). An average of six models are used in ensembles, and approximately half of ensembles weight contributions of models by their cross‐validation performance. However, discussion about choices made in the modelling process and unambiguous information on the performance of ensemble models versus individual models are limited. The use of independent data to validate model performance is particularly uncommon.
Main conclusions
We document the breadth of ensemble applications, but could not draw strong quantitative conclusions about the predictive performance of ensemble models, due to lack of unambiguous information reported. Understanding how and where ensembles are best used when modelling species distributions is important for enabling best choices for different applications. To enable this objective to be achieved, we provide recommendations for thorough reporting practices in a BIOMOD‐based ensemble workflow.
The idea that simplicity of explanation is important in science is as old as science itself. However, scientists often assume that parsimonious theories, hypothesis and models are more plausible than complex ones, forgetting that there is no empirical evidence to connect parsimony with credibility. The justification for the parsimony principle is strongly dependent on philosophical and statistical inference. Parsimony may have a true epistemic value in the evaluation of correlative and predictive models, as simpler models are less prone to overfitting. However, when natural mechanisms are explicitly modelled to represent the causes of biological phenomena, the application of the parsimony principle to judge the plausibility of mechanistic models would entail an unsupported belief that nature is simple. Here, we discuss the challenges we face in justifying, measuring, and assessing the trade‐off between simplicity and complexity in ecological and evolutionary studies. We conclude that invoking the parsimony principle in ecology and evolution is particularly important in model‐building programs in which models are viewed primarily as an operational tool to make predictions (an instrumentalist view) and in which data play a prominent role in deciding the structure of the model. However, theoretical advances in ecology and evolutionary biology may be derailed by the use of the parsimony principle to judge explanatory mechanistic models that are designed to understand complex natural phenomena. We advocate a parsimonious use of the parsimony principle.
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New remote sensing data on vegetation cover and restoration opportunities bring hope to the Brazilian Atlantic Forest, one of the hottest of the 36 global biodiversity hotspots. Available estimates of remaining vegetation cover in the biome currently range from 11% to 16%. However, our new land-cover map, prepared at the highest resolution ever (5m), reveals a current vegetation cover of 28%, or 32 million hectares (Mha) of native vegetation. Simultaneously, we found 7.2Mha of degraded riparian areas, of which 5.2Mha at least must be restored before 2038 by landowners for legislation compliance. Restoring the existing legal debt could increase native vegetation cover in the Atlantic Forest up to 35%. Such effort, if well planned and implemented, could reduce extinction processes by increasing connectivity of vegetation remnants and rising total native cover to above the critical biodiversity threshold established for different taxonomic groups. If undertaken, this process can be adaptive to climate change and boost sustainable development in this most populous biome in Brazil, turning it into a hopespot.
Poikilotherms and homeotherms have different, well-defined metabolic responses to ambient temperature (T
a
), but both groups have high power costs at high temperatures. Sloths (Bradypus) are critically limited by rates of energy acquisition and it has previously been suggested that their unusual departure from homeothermy mitigates the associated costs. No studies, however, have examined how sloth body temperature and metabolic rate vary with T
a
. Here we measured the oxygen consumption (VO2) of eight brown-throated sloths (B. variegatus) at variable T
a
's and found that VO2 indeed varied in an unusual manner with what appeared to be a reversal of the standard homeotherm pattern. Sloth VO2 increased with T
a
, peaking in a metabolic plateau (nominal 'thermally-active zone' (TAZ)) before decreasing again at higher T
a
values. We suggest that this pattern enables sloths to minimise energy expenditure over a wide range of conditions, which is likely to be crucial for survival in an animal that operates under severe energetic constraints. To our knowledge, this is the first evidence of a mammal provisionally invoking metabolic depression in response to increasing T
a
's, without entering into a state of torpor, aestivation or hibernation.
The role of improving the enforcement of Brazil’s Forest Code in reducing deforestation in the Amazon has been highlighted in many studies. However, in a context of strong political pressure for loosening environmental protections, the future impacts of a nationwide implementation of the Forest Code on both environment and agriculture remain poorly understood. Here, we present a spatially explicit assessment of Brazil’s 2012 Forest Code through the year 2050; specifically, we use a partial equilibrium economic model that provides a globally consistent national modeling framework with detailed representation of the agricultural sector and spatially explicit land-use change. We test for the combined or isolated impacts of the different measures of the Forest Code, including deforestation control and obligatory forest restoration with or without environmental reserve quotas. Our results show that, if rigorously enforced, the Forest Code could prevent a net loss of 53.4 million hectares (Mha) of forest and native vegetation by 2050, 43.1 Mha (81%) of which are in the Amazon alone. The control of illegal deforestation promotes the largest environmental benefits, but the obligatory restoration of illegally deforested areas creates 12.9 Mha of new forested area. Environmental reserve quotas further protect 5.8 Mha of undisturbed natural vegetation. Compared to a scenario without the Forest Code, by 2050, cropland area is only reduced by 4% and the cattle herd by 8%. Our results show that compliance with the Forest Code requires an increase in cattle productivity of 56% over four decades, with a combination of a higher use of supplements and an adoption of semi-intensive pasture management. We estimate that the enforcement of the Forest Code could contribute up to 1.03 PgCO2e to the ambitious GHG emissions reduction target set by Brazil for 2030
As human population, food consumption, and demand for forest products continue to rise over the next century, the pressures of land-use change on biodiversity are projected to intensify. In tropical regions, countryside habitats that retain abundant tree cover and structurally complex canopies may complement protected areas by providing suitable habitats and landscape connectivity for a significant portion of the native biota. Species with low dispersal capabilities are among the most at risk of extinction as a consequence of land-use change. We assessed how the spatial distribution of the brown-throated sloth (Bradypus variegatus), a model species for a vertebrate with limited dispersal ability, is shaped by differences in habitat structure and landscape patterns of countryside habitats in north-central Costa Rica using a multi-scale framework. We quantified the influence of local habitat characteristics and landscape context on sloth occurrence using mixed-effects logistic regression models. We recorded 27 sloths within countryside habitats and found that both local and landscape factors significantly influenced their spatial distribution. Locally, sloths favored structurally complex habitats, with greater canopy cover and variation in tree height and basal area. At the landscape scale, sloths demonstrated a preference for habitats with high proportions of forest and nearby large tracts of forest. Although mixed-use areas and tree plantations are not substitutes for protected forests, our results suggest they provide important supplemental habitats for sloths. To promote the conservation and long-term viability of sloth populations in the tropical countryside, we recommend that land managers retain structurally complex vegetation and large patches of native habitat.
Determining the susceptibility of species to changing thermal niches is a major goal for biologists. In this paper we develop an eco‐physiological model of extinction risk under climate change premised on behavioral thermoregulation. Our method downscales operative environmental temperatures, which restrict hours of activity of lizards, hr, for present‐day climate (1975) and future climate scenarios (2070). We apply our model using occurrence records of 20 Phrynocephalus lizards (or taxa in species complexes) drawn from literature and museum records. Our analysis is phylogenetically informed, because some clades may be more sensitive to rising temperatures. Computed hr limits predict local extirpations among Phrynocephalus lizards at continental scales and delineate upper boundaries of thermal niches as defined by Extreme Value Distributions. Under the 8.5 Representative Concentration Pathway scenario, we predict extirpation of 64% of local populations by 2070 across 20 Phrynocephalus species, and 12 are at high risk of total extinction due to thermal limits being exceeded. In tandem with global strategies of lower CO2 emissions, we propose regional strategies for establishing new National Parks to protect extinction‐prone taxa by preserving high‐elevation climate refugia within existing sites of species occurrence. We propose that evolved acclimatization – maternal plasticity – may ameliorate risk, but is poorly studied. Previous studies revealed that adaptive maternal plasticity by thermoregulating gravid females alter progeny thermal preferences by ±1°C. We describe plasticity studies for extinction‐prone species that could assess whether they might be buffered from climate warming – a self‐rescue. We discuss an epigenetic framework for studying such maternal‐effect evolution.
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Global climate change is expected to have strong effects on the world’s flora and fauna. As a result, there has been a recent increase in the number of meta-analyses and mechanistic models that attempt to predict potential responses of mammals to changing climates. Many models that seek to explain the effects of environmental temperatures on mammalian energetics and survival assume a constant body temperature. However, despite generally being regarded as strict homeotherms, mammals demonstrate a large degree of daily variability in body temperature, as well as the ability to reduce metabolic costs either by entering torpor, or by increasing body temperatures at high ambient temperatures. Often, changes in body temperature variability are unpredictable, and happen in response to immediate changes in resource abundance or temperature. In this review we provide an overview of variability and unpredictability found in body temperatures of extant mammals, identify potential blind spots in the current literature, and discuss options for incorporating variability into predictive mechanistic models.
Land use changes have profound effects on populations of Neotropical primates, and ongoing climate change is expected to aggravate this scenario. The titi monkeys from eastern Brazil (Callicebus personatus group) have been particularly affected by this process, with four of the five species now allocated to threatened conservation status categories. Here, we estimate the changes in the distribution of these titi monkeys caused by changes in both climate and land use. We also use demographic-based, functional landscape metrics to assess the magnitude of the change in landscape conditions for the distribution predicted for each species. We built species distribution models (SDMs) based on maximum entropy for current and future conditions (2070), allowing for different global circulation models and contrasting scenarios of greenhouse gas concentrations. We refined the SDMs using a high-resolution map of habitat remnants. We then calculated habitat availability and connectivity based on home range size and the dispersal limitations of the individual, in the context of a predicted loss of 10% of forest cover in the future. The landscape configuration is predicted to be degraded for all species, regardless of the climatic settings. This include reductions in the total cover of forest remnants, patch size and functional connectivity. As the landscape configuration should deteriorate severely in the future for all species, the prevention of further loss of populations will only be achieved through habitat restoration and reconnection to counteract the negative effects for these and several other co-occurring species. This article is protected by copyright. All rights reserved.
Primeiro Relatório de Avaliação do GT1 do PBMC 7BGMKH=NHEste documento apresenta as principais contribuições do Volume 1 do RAN1, que foi estruturado de acordo com o escopo previamente definido pelos Autores Principais dos capítulos do Grupo de Trabalho 1 (GT1). Os levantamentos aqui sintetizados resultam de uma extensa avaliação da literatura científica.existente, na qual se procurou: (i) evidenciar as implicações para o Brasil dos principais pontos do GT1 do Quarto Relatório de Avaliação (AR4) do Painel Intergovernamental de Mudanças Climáticas (IPCC, em inglês); (ii) registrar e discutir os principais trabalhos científicos publicados após 2007, com destaque para aqueles relacionados mais diretamente às mudanças climáticas na América do Sul e no Brasil.
www.pbmc.coppe.ufrj.br
Three-toed sloths (Bradypus) are heterothermic, and ambient temperature may have a direct effect on their activity levels. Our goal was to describe the time budget, pattern and rhythm of activity of the maned sloth, Bradypus torquatus (Xenarthra: Bradypodidae), and to evaluate the effect of ambient temperature on its activity. We hypothesized that (1) sloth activity increases with ambient temperature, fluctuating with the circadian temperature cycle, and (2) sloths are more active in the diurnal period during colder seasons than warm seasons due to constraints or avoidance of the colder times within a 24-h cycle. Nine radio-collared individuals were followed in forest remnants in southern Bahia, Brazil from March 2003 to April 2014. Behavior data of 8 sloths were collected during the diurnal period by direct visualization (608 h of record), and the activities of 4 sloths were recorded by an automated system during continuous hours (744 h of record). The maned sloths exhibited low activity levels, resting 77% of a 24-h period. In general, they were cathemeral, although they were twice as active in the diurnal phase (active 32% of the time) compared with the nocturnal phase (15%). The ambient temperature had a significant positive effect on activity levels. The rhythm of activity was circadian and synchronized with the ambient temperature. No difference was detected in the diurnal activity between hotter and colder seasons, most likely reflecting the low fluctuations in climatic conditions of this tropical forest. The narrow relationship between the circadian activity pattern of maned sloths and the ambient temperature cycle highlights their poor thermoregulatory ability. The lower activity levels exhibited during colder times may represent a behavioral adaptation that reduces heat loss, enhances body temperature control and optimizes energetic benefits, a key feature for a species relying on a low energetic diet.
The vast terrain between Panama and Tierra del Fuego contains some of the worldâs richest mammalian fauna, but until now it has lacked a comprehensive systematic reference to the identification, distribution, and taxonomy of its mammals. The first such book of its kind and the inaugural volume in a three-part series, Mammals of South America both summarizes existing information and encourages further research of the mammals indigenous to the region. Containing identification keys and brief descriptions of each order, family, and genus, the first volume of Mammals of South America covers marsupials, shrews, armadillos, sloths, anteaters, and bats. Species accounts include taxonomic descriptions, synonymies, keys to identification, distributions with maps and a gazetteer of marginal localities, lists of recognized subspecies, brief summaries of natural history information, and discussions of issues related to taxonomic interpretations.Highly anticipated and much needed, this book will be a landmark contribution to mammalogy, zoology, tropical biology, and conservation biology.
The mechanistic links between climate and the environmental sensitivities of organisms occur through the microclimatic conditions that organisms experience. Here we present a dataset of gridded hourly estimates of typical microclimatic conditions (air temperature, wind speed, relative humidity, solar radiation, sky radiation and substrate temperatures from the surface to 1 m depth) at high resolution (~15 km) for the globe. The estimates are for the middle day of each month, based on long-term average macroclimates, and include six shade levels and three generic substrates (soil, rock and sand) per pixel. These data are suitable for deriving biophysical estimates of the heat, water and activity budgets of terrestrial organisms.
The effects of climate change on biodiversity are increasingly well documented, and many methods have been developed to assess species' vulnerability to climatic changes, both ongoing and projected in the coming decades. To minimize global biodiversity losses, conservationists need to identify those species that are likely to be most vulnerable to the impacts of climate change. In this Review, we summarize different currencies used for assessing species' climate change vulnerability. We describe three main approaches used to derive these currencies (correlative, mechanistic and trait-based), and their associated data requirements, spatial and temporal scales of application and modelling methods. We identify strengths and weaknesses of the approaches and highlight the sources of uncertainty inherent in each method that limit projection reliability. Finally, we provide guidance for conservation practitioners in selecting the most appropriate approach(es) for their planning needs and highlight priority areas for further assessments.
Habitat selection is a scale-dependent process of paramount importance to the understanding of how species deal with environmental variation. This process has practical implications for wildlife conservation, aiding in the identification of key resources for animals and in the definition of scales relevant to the proposal of practical conservation actions. In this study, we investigated in different spatial scales the habitat selection of the maned three-toed sloth (Bradypus torquatus), a threatened and endemic arboreal folivore of the Atlantic rainforest (vulnerable, sensu IUCN). We radio-tracked and monitored seven sloths for 18 months in landscapes of Southern Bahia, Brazil, the current core region of the species’ distribution. The average values of the home-range estimates were low, but varied considerably among individuals regardless of the estimator (from 0.95 to 27.8 ha, MCP method, and from 0.39 to 21.52 ha, fixed kernel method). At the landscape scale, the maned sloths preferred early secondary forest and shade cacao plantations, avoided open areas, and occupied late secondary forest as expected compared to its availability. At the home range scale, however, the sloths did not show preference for any forest category, though, again, avoided open areas. At smaller spatial scales, the sloths were highly selective towards forest patches characterized by complex vegetation structures (i.e., areas with a high density of trees, closed and dense canopies), and selected large trees with lianas and bromeliads and also with connected crowns. The high selectivity observed at finer scales appeared to be the result of limited spatial perception and experience due to the species’ characteristic slow mobility. Our results support the notion that maned sloths can effectively occupy (and even select for) disturbed forested habitats. However, we do not know whether sloth populations are viable in landscapes containing only disturbed habitats or low proportions of undisturbed habitats.
The impact of anthropogenic climate change on terrestrial organisms is often predicted to increase with latitude, in parallel with the rate of warming. Yet the biological impact of rising temperatures also depends on the physiological sensitivity of organisms to temperature change. We integrate empirical fitness curves describing the thermal tolerance of terrestrial insects from around the world with the projected geographic distribution of climate change for the next century to estimate the direct impact of warming on insect fitness across latitude. The results show that warming in the tropics, although relatively small in magnitude, is likely to have the most deleterious consequences because tropical insects are relatively sensitive to temperature change and are currently living very close to their optimal temperature. In contrast, species at higher latitudes have broader thermal tolerance and are living in climates that are currently cooler than their physiological optima, so that warming may even enhance their fitness. Available thermal tolerance data for several vertebrate taxa exhibit similar patterns, suggesting that these results are general for terrestrial ectotherms. Our analyses imply that, in the absence of ameliorating factors such as migration and adaptation, the greatest extinction risks from global warming may be in the tropics, where biological diversity is also greatest.
• biodiversity
• fitness
• global warming
• physiology
• tropical
Spatial thinning of species occurrence records can help address problems associated with spatial sampling biases. Ideally, thinning removes the fewest records necessary to substantially reduce the effects of sampling bias, while simultaneously retaining the greatest amount of useful information. Spatial thinning can be done manually; however, this is prohibitively time consuming for large datasets. Using a randomization approach, the ‘thin’ function in the spThin R package returns a dataset with the maximum number of records for a given thinning distance, when run for sufficient iterations. We here provide a worked example for the Caribbean spiny pocket mouse, where the results obtained match those of manual thinning.
The authors assess the ability of 18 Earth system models to simulate the land and ocean carbon cycle for the present climate. These models will be used in the next Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) for climate projections, and such evaluation allows identification of the strengths and weaknesses of individual coupled carbon–climate models as well as identification of systematic biases of the models. Results show that models correctly reproduce the main climatic variables controlling the spatial and temporal characteristics of the carbon cycle. The seasonal evolution of the variables under examination is well captured. However, weaknesses appear when reproducing specific fields: in particular, considering the land carbon cycle, a general overestimation of photosynthesis and leaf area index is found for most of the models, while the ocean evaluation shows that quite a few models underestimate the primary production .The authors also propose climate and carbon cycle performance metrics in order to assess whether there is a set of consistently better models for reproducing the carbon cycle. Averaged seasonal cycles and probability density functions (PDFs) calculated from model simulations are compared with the corresponding seasonal cycles and PDFs from different observed datasets. Although the metrics used in this study allow identification of some models as better or worse than the average, the ranking of this study is partially subjective because of the choice of the variables under examination and also can be sensitive to the choice of reference data. In addition, it was found that the model performances show significant regional variations.
It is predicted that climate change will cause species extinctions and distributional shifts in coming decades, but data to
validate these predictions are relatively scarce. Here, we compare recent and historical surveys for 48 Mexican lizard species
at 200 sites. Since 1975, 12% of local populations have gone extinct. We verified physiological models of extinction risk
with observed local extinctions and extended projections worldwide. Since 1975, we estimate that 4% of local populations have
gone extinct worldwide, but by 2080 local extinctions are projected to reach 39% worldwide, and species extinctions may reach
20%. Global extinction projections were validated with local extinctions observed from 1975 to 2009 for regional biotas on
four other continents, suggesting that lizards have already crossed a threshold for extinctions caused by climate change.
The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides policymakers with regular assessments of the scientific basis of human-induced climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the most comprehensive and up-to-date assessment of the observed and projected changes to the ocean and cryosphere and their associated impacts and risks, with a focus on resilience, risk management response options, and adaptation measures, considering both their potential and limitations. It brings together knowledge on physical and biogeochemical changes, the interplay with ecosystem changes, and the implications for human communities. It serves policymakers, decision makers, stakeholders, and all interested parties with unbiased, up-to-date, policy-relevant information. This title is also available as Open Access on Cambridge Core.
Different models are available to estimate species’ niche and distribution. Mechanistic and correlative models have different underlying conceptual bases, thus generating different estimates of a species’ niche and geographic extent. Hybrid models, which combining correlative and mechanistic approaches, are considered a promising strategy, however, no synthesis in the literature assessed their applicability for terrestrial vertebrates to allow best-choice model considering their strengths and trade-offs. Here, we provide a systematic review of studies that compared or integrated correlative and mechanistic models to estimate species’ niche for terrestrial vertebrates under climate change. Our goal was to understand their conceptual, methodological, and performance differences, and the applicability of each approach. The studies we reviewed directly compared mechanistic and correlative predictions in terms of accuracy or estimated suitable area, however, without any quantitative analysis to support comparisons. Contrastingly, many studies suggest that instead of comparing approaches, mechanistic and correlative methods should be integrated (hybrid models). However, we stress that the best approach is highly context-dependent. Indeed, the quality and effectiveness of the prediction depends on the study's objective, methodological design, and which type of species’ niche and geographic distribution estimated are more appropriate to answer the study's issue.
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Ecophysiological models are more data demanding and, consequently, less used than correlative ecological niche models to predict species’ distribution under climate change, especially for endotherms. Hybrid models that integrate both approaches are even less used, and several aspects about their predictions (e.g. accuracy, geographic extent and uncertainty) have been poorly explored. We developed a hybrid model for mammals using hours of activity and hours of heat stress as mechanistic variables, fitted using macroclimatic data and applied to conventional correlative modeling. We then compared the outputs from conventional correlative models with our hybrid model for 58 tropical mammals in term of accuracy, uncertainty, and predicted geographic distribution under climate change. We expected that hybrid models to have higher accuracy than correlative ones, with difference in predicted geographic distribution extent. We found no substantial differences between correlative and hybrid predictions for accuracy, uncertainty, and extent. Although the area predicted as suitable did not differ in extent, they differ in location, with lower congruence between models for future prediction. This result challenged the widespread assumption that hybrid models are more accurate. The ecophysiological model approach proposed here ease ecophysiological data requirements. We propose, therefore, choosing model approach based on study's objective, rather than on data requirements or the assumption that hybrid models have better predictions. The main advantage of the hybrid model is in providing a more complete view of the species response, as proximal (causal) and distal (environment) aspects are combined.
Climate and land-use change are major drivers of biodiversity loss, but their combined effects are still unclear. Reforestation may compensate or reduce climate change impacts on species, but this hypothesis has not been tested yet. Here we quantify the additive and synergistic effects of forest change-in particular, reforestation-and climate changes on ten endemic and forest-dependent anurans of the Atlantic Forest biodiversity hotspot. We estimated climatic and habitat suitability for all species under historical and future (2050) conditions, using niche modeling and forest cover maps from a comprehensive land-use model. We contrasted a pessimistic land-use scenario, with little change in forest cover, with an optimistic scenario, with forest gain through restoration of "legal reserve" areas. Our models show that climate change will have species-specific effects on anurans, increasing climatic suitability for seven species, but decreasing for three. For these three species, we predict that forest gain can compensate the negative impact of climate change, increasing overall environmental suitability. These results reinforce the importance of ensuring reforestation and forest protection as a climate change adaptation strategy for biodiversity.
• In addition to being threatened by habitat loss derived from deforestation and urbanisation, fireflies are further deeply impacted by light pollution, which impairs their unique use of light signals to communicate and track females. The impact of stressors that can lead to declines in firefly populations is poorly known in the southern hemisphere, including the Atlantic Forest where they are especially diverse, associated with lack of knowledge about their distributions.
• Here, we model the potential distribution of the tracker ghost firefly Amydetes fastigiata and investigate whether light pollution, urbanisation and deforestation are increasing over time in this area.
• We found that light pollution is the stressor with the most prominent increase rates over its distribution. Light pollution is significantly increasing in extent and intensity over time, outpassing urbanisation and deforestation which increased at lower rates. Protected areas successfully buffer effects of urbanisation and deforestation, but are incapable to halt the spread of light pollution.
• Increasing light pollution is especially concerning due to the spotlighting behaviour of A. fastigiata to track females through the night, which is imperilled by overshadowing lights. Light pollution trends are increasing fast and should be considered as a significant stressor even within protected areas – which calls for a reform in regional conservation policies and designation of new areas to be prioritised.
• We presented a framework for the evaluation of threat rates based on species distribution models that can foster future research and assess vulnerabilities of important species facing global change.
Temperature is an important environmental factor governing the ability of organisms to grow, survive and reproduce. Thermal performance curves (TPCs), with some caveats, are useful for charting the relationship between body temperature and some measure of performance in ectotherms, and provide a standardized set of characteristics for interspecific comparisons. Endotherms, however, have a more complicated relationship with environmental temperature, as endothermy leads to a decoupling of body temperature from external temperature through use of metabolic heat production, large changes in insulation and variable rates of evaporative heat loss. This has impeded our ability to model endothermic performance in relation to environmental temperature as well as to readily compare performance between species. In this Commentary, we compare the strengths and weaknesses of potential TPC analogues (including other useful proxies for linking performance to temperature) in endotherms and suggest several ways forward in the comparative ecophysiology of endotherms. Our goal is to provide a common language with which ecologists and physiologists can evaluate the effects of temperature on performance. Key directions for improving our understanding of endotherm thermoregulatory physiology include a comparative approach to the study of the level and precision of body temperature, measuring performance directly over a range of body temperatures and building comprehensive mechanistic models of endotherm responses to environmental temperatures. We believe the answer to the question posed in the title could be ‘yes’, but only if ‘performance’ is well defined and understood in relation to body temperature variation, and the costs and benefits of endothermy are specifically modelled.
The Atlantic Forest is one of the 36 hotspots for biodiversity conservation worldwide. It is a unique, large biome (more than 3000 km in latitude; 2500 in longitude), marked by high biodiversity, high degree of endemic species and, at the same time, extremely threatened. Approximately 70% of the Brazilian population lives in the area of this biome, which makes the conflict between biodiversity conservation and the sustainability of the human population a relevant issue. This book aims to cover: 1) the historical characterization and geographic variation of the biome; 2) the distribution of the diversity of some relevant taxa; 3) the main threats to biodiversity, and 4) possible opportunities to ensure the biodiversity conservation, and the economic and social sustainability. Also, it is hoped that this book can be useful for those involved in the development of public policies aimed at the conservation of this important global biome.
Ongoing anthropogenic climate change is becoming one of the major threats to biodiversity. Studies that aim at projecting the future impacts of ongoing climate change on biodiversity should use general circulation models (GCMs) that show a good performance in the region of study, an information that is lacking for the Atlantic Forest. Here, we evaluated the performance of different GCMs over the Atlantic Forest, describe the predicted climatic changes for the regions based on the best performing GCMs, review the literature on observed and predicted impacts of climate change on the Atlantic Forest biodiversity, and discuss adaptation strategies to reduce the negative impacts of climate change on the region’s biodiversity.
How climate constrains species’ distributions through time and space is an important question in the context of conservation planning for climate change. Despite increasing awareness of the need to incorporate mechanism into species distribution models (SDMs), mechanistic modelling of endotherm distributions remains limited in the current literature. Using the American pika (Ochotona princeps) as an example, we present a framework whereby mechanism can be incorporated into endotherm SDMs. Pika distribution has repeatedly been found to be constrained by warm temperatures, so we used Niche Mapper, a mechanistic heat-balance model, to convert macroclimate data to pika-specific surface-activity time in summer across the western United States. We then explored the difference between using a macroclimate predictor (summer temperature) and using a mechanistic predictor (predicted surface-activity time) in SDMs. Both approaches accurately predicted pika presences in current and past climate regimes. However, the activity models predicted 8-19% less habitat loss in response to annual temperature increases of ~3-5°C predicted in the region by 2070, suggesting that pikas may be able to buffer some climate-change effects through behavioral thermoregulation that can be captured by mechanistic modeling. Incorporating mechanism added value to the modeling by providing increased confidence in areas where different modeling approaches agreed and providing a range of outcomes in areas of disagreement. It also provided a more proximate variable relating animal distribution to climate, allowing investigations into how unique habitat characteristics and intraspecific phenotypic variation may allow pikas to exist in areas outside those predicted by generic SDMs. Only a small number of easily obtainable data are required to parameterize this mechanistic model for any endotherm, and its use can improve SDM predictions by explicitly modeling a widely applicable direct physiological effect: climate-imposed restrictions on activity. This more complete understanding is necessary to inform climate-adaptation actions, management strategies, and conservation plans. This article is protected by copyright. All rights reserved.
The Paris climate agreement aims at holding global warming to well below 2 degrees Celsius and to “pursue efforts” to limit it to 1.5 degrees Celsius. To accomplish this, countries have submitted Intended Nationally Determined Contributions (INDCs) outlining their post-2020 climate action. Here we assess the effect of current INDCs on reducing aggregate greenhouse gas emissions, its implications for achieving the temperature objective of the Paris climate agreement, and potential options for overachievement. The INDCs collectively lower greenhouse gas emissions compared to where current policies stand, but still imply a median warming of 2.6–3.1 degrees Celsius by 2100. More can be achieved, because the agreement stipulates that targets for reducing greenhouse gas emissions are strengthened over time, both in ambition and scope. Substantial enhancement or over-delivery on current INDCs by additional national, sub-national and non-state actions is required to maintain a reasonable chance of meetin
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Species distribution models (SDMs) are widely used to explain and predict species ranges and environmental niches. They are most commonly constructed by inferring species' occurrence–environment relationships using statistical and machine-learning methods. The variety of methods that can be used to construct SDMs (e.g. generalized linear/additive models, tree-based models, maximum entropy, etc.), and the variety of ways that such models can be implemented, permits substantial flexibility in SDM complexity. Building models with an appropriate amount of complexity for the study objectives is critical for robust inference. We characterize complexity as the shape of the inferred occurrence–environment relationships and the number of parameters used to describe them, and search for insights into whether additional complexity is informative or superfluous. By building ‘under fit’ models, having insufficient flexibility to describe observed occurrence–environment relationships, we risk misunderstanding the factors shaping species distributions. By building ‘over fit’ models, with excessive flexibility, we risk inadvertently ascribing pattern to noise or building opaque models. However, model selection can be challenging, especially when comparing models constructed under different modeling approaches. Here we argue for a more pragmatic approach: researchers should constrain the complexity of their models based on study objective, attributes of the data, and an understanding of how these interact with the underlying biological processes. We discuss guidelines for balancing under fitting with over fitting and consequently how complexity affects decisions made during model building. Although some generalities are possible, our discussion reflects differences in opinions that favor simpler versus more complex models. We conclude that combining insights from both simple and complex SDM building approaches best advances our knowledge of current and future species ranges.
Ecological niche models represent key tools in biogeography but the effects of biased sampling hinder their use. Here, we address the utility of two forms of filtering the calibration data set (geographic and environmental) to reduce the effects of sampling bias. To do so we created a virtual species, projected its niche to the Iberian Peninsula and took samples from its binary geographic distribution using several biases. We then built models for various sample sizes after applying each of the filtering approaches. While geographic filtering did not improve discriminatory ability (and sometimes worsened it), environmental filtering consistently led to better models. Models made with few but climatically filtered points performed better than those made with many unfiltered (biased) points. Future research should address additional factors such as the complexity of the species’ niche, strength of filtering, and ability to predict suitability (rather than focus purely on discrimination).
The maned sloth is a poorly known species endemic to the highly fragmented and disturbed Brazilian Atlantic forest. As this species has a strictly forest habitat and low dispersion ability, it is susceptible to local extinctions in small and isolated fragments. The project started in 1994, translocating stranded sloths found within or nearby urban zones into forest reserves located in Santa Teresa, state of Espı́rito Santo. Five translocated, radio-collared adults were monitored monthly from periods lasting from 10 months to 3 years after release and data on activity budgets, diet, and home range size were analysed. Results showed that moving and feeding time and distances travelled daily were not significantly related to translocation time (i.e., time, in days, after release). One female, monitored for three years showed, however, a steady and significant decrease in time spent moving from the first to the second to the third year of monitoring (regression Analysis; p0.05). Sloths explored the area more intensively in the first 6 months after release, but minor changes in home ranges were detected even after 3 years. Results suggest that maned sloths are amenable to translocation experiments provided that source and release sites are floristic and ecologically similar. To fully access the success of such experiments though, it is recommended that sloths be monitored for periods longer than 1 year.