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Predicting Extinction Risk:
The Importance of Life History and Demography

By Claire Asher, on 28 July 2014

The changing climate is no longer simply a concern for the future, it is a reality. Understanding how the biodiversity that we share our planet with will respond to climate change is a key step in developing long-term strategies to conserve it. Recent research by UCL CBER’s Dr Richard Pearson identifies the key characteristics that are likely to influence extinction risk due to climate change, and shows that existing conservation indicators such as the IUCN red list may contain the data necessary to make these predictions.

Human activities have been negatively impacting biodiversity for centuries, and conservationists have developed a number of different indicator lists which attempt to classify species’ extinction risk. However, these lists were created to measure human impacts such as as habitat loss, hunting and introduction of invasive species. These impacts will continue to be a major issue for biodiversity, but may be dwarfed in the future as climate change takes hold. Can the indices and data we already have be used to predict extinction risk from climate change? Or does climate change represent a new type of threat, needing new indices?

Studies have previously identified the ecological and biological traits that are characteristic of threatened or declining species. However, it is not clear how well these traits predict the future risk of climate-induced extinction. In February this year, GEE’s Dr Richard Pearson, in collaboration with colleagues at the American Museum of Natural History, Stony Brook University and the University of Adelaide, published a paper in Nature which attempted to address these questions. Most studies that have considered the impact of climate change on species’ extinctions have attempted to predict changes in the distribution of suitable habitats and measure extinction risk in terms of whether the species is likely to be able to find habitat to live in. However, such studies rarely consider how a species’ traits such as life history and spatial characteristics will influence their ability to persist through changes in climate. In this study, Pearson and colleagues coupled ecological niche models with demographic models, and developed a generic life history method to estimate extinction risk over the coming century.

Modelling Extinction
The authors then tested their models on ecological and spatial traits for 36 reptile and amphibian species in the USA. Using commonly available life history variables, they found that their models could accurately predict extinction risk between 2000 and 2010. They then utilised the same traits and models to predict future extinction risk under two climate models – a high emissions scenario and a policy scenario aimed at curbing emissions. Average extinction risk for the 36 species studied was 28% under the high emissions scenario, dropping to 23% under strict policy intervention. This seems like a very small difference for a significant intervention – it’s important to note that the same estimates indicated an average extinction risk of just 1% in the absence of any climate change at all.

One of the most important determinants of extinction risk in reptiles and amphibians was occupied area, which represents the range of climatic and habitat conditions the species can survive in. Species with a larger occupied area tended to be more robust to climate change, presumably because they are already adapted to a wider range of habitats and climates. Other key variables influencing extinction risk include population size and generation length. In many cases, traits interacted to determine species risk, for example extinction risk was strongly influenced by interactions between occupied area and generation length. Including many different traits can therefore greatly improve the accuracy of predictions. Recent trends tended to be less informative than spatial, demographic and life history traits, particularly under the high emissions scenario, suggesting that the impacts of climate change we have observed so far are likely to become less and less relevant as climate change accelerates.

The majority of variables that showed a significant impact on extinction risk are already included in major conservation assessments and indices, meaning that data and monitoring programs already in place may be better at predicting extinction risk under climate change than we might have expected. Climate change may not be fundamentally different from other human threats such as habitat loss and hunting, at least in terms of our ability to assess extinction risk. Conservation initiatives should focus on species who currently occupy a small and declining area and have a small population size. Regardless of the policy future, conservation actions will need to consider and account for climate change if they are to prove effective.

Original Article:

() Life History and Spatial Traits Predict Extinction Risk Due to Climate Change Nature

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This research was made possible by funding from the National Aeronautics and Space Administration (NASA) and the Australian Research Council

Biological Traits Influence Vulnerability to Climate Change in Birds, Amphibians and Corals

By Claire Asher, on 25 June 2013

Climate change is fast becoming a reality, and with temperature rises of between 0.8°C and 2.6°C predicted over the next 35 years, biodiversity will certainly be impacted, with many species set to suffer declines or potential extinction. But all species are not equal and certain traits may make species more or less vulnerable to climate change than others. A new model presented in PLOS one this month investigates the impact of biological traits, such as physiology, ecology and evolutionary history, on vulnerability to climate change for some of the most threatened groups: birds, amphibians and corals. Around 10% of species are both highly vulnerable to climate change, and already listed as threatened with extinction. The model also identifies potentially vulnerable species for future conservation priorities, giving biologists a head-start in trying to slow the inevitable loss of biodiversity that climate change will bring.

Many researchers are interested in predicting how biodiversity might respond to climate change. Biodiversity is essential to human survival – diverse, functional ecosystems provide us with food, water and medicine. However, predicting how ecosystems might respond to changes in temperature and rainfall is a complicated matter. Most previous models have considered the availability of suitable habitat for species based upon their current range and predictions of temperature changes. However, not all species are created equal – biological traits of individual species are likely to play an important role in determining species survival. For example, some species are adapted to a very specialised habitat or are poor as dispersal and so may struggle to find alternative habitats even if they are available. Other species have long generation times and produce few young, or have very limited genetic diversity in the population, making adaptation to new habitats more difficult. Species like these are likely to be more vulnerable to climate change than generalists who are good at dispersal and produce lots of offspring. Not considering the biology of a species when modelling responses to climate change can lead to under- or over-estimations of how vulnerable a species actually is.

Accounting for Biology
To address this issue, Foden and colleagues, working in collaboration with Professor Georgina Mace from CBER, developed a systematic framework for assessing species vulnerability to climate change, and applied this model to three of the best-studied, and most endangered groups of animals: birds, amphibians and corals. They considered three factors – sensitivity (whether a species can survive where it is), exposure (the predicted extent of change under climate models), and adaptive capacity (whether a species can avoid the negative impacts of climate change by moving or evolving).

The components of species vulnerability - sensitivity, adaptive capacity and exposure

Components of species
vulnerability – sensitivity, adaptive
capacity and exposure

In consultation with extinction risk specialists, they identified 90 biological, ecological, phsyiolocial and environmental traits which are likely to influence vulnerability to climate change. In particular, they identified habitat specialisation, rarity, environmental tolerance, disruption of environmental triggers and interactions with other species as key components of species sensitivity to climate change. Adaptive capacity is composed of dispersal ability, barriers to dispersal, genetic diversity, generation length and reproductive output. They assessed these traits for each of 16,857 species of bird, amphibian and coral, across the globe.

The proportion of species in a region that are sensitive or have limited adaptive capacity (blue), high exposure to climate change (yellow) or both (maroon).

The proportion of species in a region that are sensitive or have limited adaptive capacity (blue), high exposure to climate change (yellow) or both (maroon).

Armed with these traits, they were able to determine sensitivity, adaptive capacity and exposure for each species, and generated maps of where species may be particularly vulnerable. They found that around 24% – 50% of bird species, 22% – 44% of amphibians and 15% – 32% of corals are both sensitive and exposed, and have limited capacity to adapt. They identified the Amazon region as containing many highly vulnerable birds and amphibians. Many bird species were also highly vulnerable in central Eurasia, the Congo basin, the Himalayas, Malaysia and Indonesia, with amphibians most vulnerable in north Africa, eastern Russia, and the northern Andes. The waters around Malaysia, Indonesia and the Philippines were hot-spots for highly vulnerable corals.

A Silver Lining
It’s not all doom and gloom, though. The study also identified some species and regions where species’ traits may make them more able to cope with climate change. Around 28% -53% of bird species, 23% – 59% of amphibians and 30% – 55% of corals may survive projected climate changes because of their inherent ability to disperse or adapt to change. In particular, southern Asia and North America may see less severe biodiversity declines than previously thought.

The interplay between climate change and biodiversity is complex, and unlikely to be uniform across taxonomic groups. It is important to consider the physiological, ecological and evolutionary traits of individual species when making predictions about the impact of climate change. This study considered the effects of temperature and rainfall changes, as well as ocean acidification and sea-level rise, on global biodiversity. However, many other factors will influence whether species survive over the long-term – habitat destruction, invasive species and pollution are also major drivers of extinction which need to be taken into account when predicting the future of a species. Taking into account the biology of a species, and it’s interaction with other species, is a major step forward in our understanding of how biodiversity will respond to the impending climate changes that are now inevitable.

Original Article:

This research was made possible by funding from the MacArthur Foundation.

Farewell to One of Darwin’s Frogs
…but it’s not too late for another

By Claire Asher, on 18 June 2013

Amphibian declines are one of the biggest conservation concerns of the 21st century. In a paper last week in PLOS ONE, Claudio Soto-Azat at the Universidad Andrés Bello in Chile, in collaboration with Ben Collen from GEE’s Centre for Biodiversity and Environmental Research (CBER), and colleagues at ZSL, reported some sad news about two species of Darwin’s frog in South American. They announce the exctintion of the Chile Darwin’s Frog and substantial declines in the closely related species, Darwin’s Frog.

Using published data and archived specimens, Soto-Azat and colleagues reconstructed the historical range of these two species across Chile and Argentina, and went looking for the frogs right across their original range. Not a single Chilea Darwin’s frog (Rhinoderma rufum) was found. They used modeling based upon recorded sightings to predict whether the Chile Darwin’s frog truly is extinct. Unfortunately, this model confirmed the worst, that Chile Darwin’s frog is now extinct in the wild, and probably vanished over 30 years ago.

Darwin’s Frog (Rhinoderma darwinii)
Image from ARKive. Photograph used with permission from (Universidad Andrés Bello)

Populations of the closely related Darwin’s frog (Rhinoderma darwinii) were found, however these populations are much smaller and more fragmented than previously thought. The authors recommend classifying Darwin’s only remaining frog as Endangered. No frogs were found in or near urban environments – the surviving populations exist in primary forest. The populations that have gone extinct had been put under strain from human pressures. In Chile, loss of native forest as it is chopped down to make way for pine plantations to satisfy a growing global demand for wood and paper may be reducing the availability of habitat for these colourful little frogs.

The same frog captured twice during the study - identifiable by it's unique underbelly patterning

Darwin’s Frog (Rhinoderma darwinii)
The same frog captured twice – identifiable by it’s unique underbelly patterning

Darwin’s frogs aren’t just colourful, they also have a rather remarkable way to care for their young. The male waits patiently until the eggs he fertilised are ready to hatch, when he swallows the eggs and holds them in his vocal sac as they hatch. The tadpoles remain their at least until they are able to feed by themselves, but in Darwin’s frog (R.darwinii), the young stay until they can hop out, as tiny froglets. Chile Darwin’s frog is lost forever, but it may not be too late to save Darwin’s frog, and this unusual strategy for rearing offspring.

Original Article:

() PLOS ONE