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The Delicate Balance of Effect and Response

By Claire Asher, on 18 February 2014

We may not always be aware of it, but many wild plants, animals, fungi and even bacteria, provide crucial services to us which keep the ecosystems of Earth functioning. Environmental changes caused by human activities are now threatening many species, and those that cannot withstand these changes may be lost forever, potentially taking the services they provide away. New research from GEE and collaborators worldwide aims to improve our understanding of how the traits and evolutionary histories of species influence their ability to provide essential ecosystem services, and to persist in the face of ongoing environmental change.

The diverse array of species we share planet Earth with, and the complex ecosystems they form, are crucial to our continued survival and well being. Species and ecosystems provide a huge number of ‘ecosystem services’ – functions such as nutrient cycling, waste decomposition, pollination and food, to name just a few, which humans rely on. However, many species are now under threat from human activities like deforestation, hunting and pollution. Scientists are working to understand how species and ecosystems will respond to our continued activities in the future, and particularly how this may effect the vital ecosystem services upon which we rely. Recent research by GEE’s Prof. Georgina Mace, in collaboration with researchers from Cordoba National Univerity, Imperial College London, VU University, Yale University and CSIC, has attempted to develop a new framework for risk assessing the effect of human activities on ecosystem services.

The framework considers two key aspects of species: their effect on the generation of a specific ecosystem service (e.g. seed dispersal), and their response to specific environmental pressures (e.g. drought). Both the effect of a species and the response of a species are underpinned by its traits, and each is influenced not by a single trait but a combination of traits. The response of a species will determine it’s ability to survive and flourish through future environmental changes and to continue to provide it’s ecosystem effects. However, only a species’ response is the subject of natural selection, via changes to the underlying traits; the effect of a species is merely a biproduct of traits selected for their influence on survival. In this way, the aspects of a species’ biology upon which we rely are only indirectly influenced by natural selection, and will only be maintained if the traits that generate them are beneficial through the environmental changes we cause. The framework developed by GEE researchers and collaborators considers how the response of species to envinmental stressors interacts with the effect of that species on key ecosystem services, and whether species with a large effect are more or less vulnerable to environmental change.

A third key factor influencing the sensitivity of ecosystem system services is the evolutionary relationships between species providing them. Closely related species often share similar traits, which may or may not result in them having similar effects and responses. If this is the case, then ecosystems in which a particular service is provided by a group of closely related species may be more vulnerable to environmental change, since those species may well share similar responses, and be sensitive to similar environmental pressures. Although many species’ traits are known to be similar amongst related species, because effects and responses are each the result of a combination of traits, it is not known whether this relationship is also common for these variables.

The new framework developed by GEE’s Professor Georgina Mace and collaborators attempts to address this by incorporating evolutionary relationships (phylogeny) into their response-effect model, and applying this model to 5 case studies. The case studies cover 5 species assemblages including a total of 480 species in Europe, Central America and Africa, for which response and effects could be estimated based on past studies of species’ traits and vulnerabilities. The case studies tended to show a strong relationship between phylogeny and both species’ effects on ecosystem services and their responses to environmental stressors. This indeed suggests that ecosystem services that rely upon closely related groups of species may be most at risk from environmental change. Cases where effects and responses are negatively correlated, so that the most influential species in terms of a given ecosystem service are also the most vulnerable to environmental stress, are most vulnerable to loss of that ecosystem service through human activities. Whether this type of relationship is common in nature remains to be investigated by future studies, and this framework provides a powerful basis with which to do so.

Our relentless demands on the natural world are inevitably leading to new pressures and stresses on natural populations, and it is of great concern that these pressures may negatively impact on the vital ecosystem services that we rely upon, often without even realising it. Ecosystem services provide us with food and fresh water, decompose our waste, recycle nutrients and remove harmful toxins. Without them our continued survival and well being would be seriously compromised. Scientists are still working to understand how species’ traits influence their ability to provide ecosystem services and their resilience to ongoing environmmental change. A new framework developed in collaboration between universities in the UK, Spain, Argentina, the USA and the Netherlands is beginning to shed light on the interaction between species’ traits, their effect on ecosystem services and their response to environmental change, and how these factors are influenced by evolutionary relationships between species. This framework offers a powerful new view of how the traits of species within an ecosystem translate into the ecosystem services upon which we are so reliant, and future research building upon this framework promises to improve our understanding of ecosystem services and environmental change.

Original Article:

() Ecology and Evolution



This research was made possible by funding from the Natural Environment Research Council (NERC), the Leverhulme Trust, and the US National Science Foundation

Predicting the Future of Biodiversity

By Claire Asher, on 14 August 2013

As human populations expand and use the land differently, they are having an impact on the plants and animals that share that land with them. Conservation biologists have been working for decades to try and document the ways in which these changes are affecting species, and to try and develop indicators that can be used to monitor these changes over time. However, previous work has tended to focus on certain species (e.g. bats, birds), neglecting other important groups such as insects, and have been biased towards certain habitats (e.g. tropical rainforest).

A new project in partnership between University College London, Imperial College London, the University of Sussex, UNEP World Conservation Monitoring Center and Microsoft Research, aims to improve on previous studies and develop a model for understanding how whole biological communities respond to human pressures across the globe. Collating high-quality data from hundreds of peer-reviewed papers, in addition to unpublished data direct from field researchers, the PREDICTS team hope to investigate local patterns of biodiversity at a global scale, and improve our understanding of how whole ecosystems respond to human pressures such as land-use change.

Biodiversity Declines
IMG_5921Major global loss of biodiversity is underway, and we have good reason to believe humans are responsible. The current extinction rate of species is estimated to be 1000 times higher than long-term historical averages, although large fluctuations in this in the past were also common. Humans have altered the world enormously, converting forests and savannas into farmland and housing. Virtually all ecosystems have been changed substantially – most biomes have lost between 20 and 50% of land to human uses. Humans have also exploited natural resources for wood, food, medicine and social reasons, and in many cases overexploitation has lead to major species declines and extinctions. Globally, it is estimated that 12% of bird species, 23% of mammals and 32% of amphibians are threatened with extinction, with many of these species suffering population declines and a reduction in genetic diversity, which may exacerbate the effect of human impacts. Even optimistic projections indicate continued human pressure on biodiversity from a range of different sources including hunting and habitat destruction. Many of the pressures currently placed on global biodiversity, such as land-use change, pollution and the introduction of invasive species, are set to continue or intensify over coming decades.

Ecosystem Services
Biodiversity is a valuable asset to humans for many reasons, not least its considerable economic value. Biodiversity contributes to human well-being by providing ecosystem services such as food (crops and livestock), fresh water, timber, natural hazard protection, air quality, climate regulation, prevention of erosion, as well as cultural benefits such as the aesthetic and recreational use of biodiversity. The exact relationship between biodiversity and ecosystem services is still relatively poorly understood, as it represents a complex interaction of many factors, which may vary from habitat to habitat. Many researchers suspect there may be threshold effects, with a sudden collapse of ecosystems, and a consequent loss of the services they provide, once a threshold number of species is lost. Others suggest certain ‘keystone’ species may be more important for ecosystem function. What is clear, however, is that healthy, functioning ecosystems are key to human health and well being. A greater understanding both of how biodiversity contributes to ecosystem function and ecosystem services, and of how biodiversity is likely to respond to continued anthropogenic pressures is sorely needed.

Improving Indicators
DSC_1216_watermarkOne central issue to studying and increasing our understanding of how ecosystems respond to human pressures is selecting species, populations or ecosystems to act as indicators of overall trends. It is simply not possible to monitor all populations of all species, and conservationists have traditionally relied upon indicator species and ecosystems as a measure of the overall health of biodiversity. In many cases these indicators were initially selected out of convenience meaning that well-studied species, communities and biomes are hugely overrepresented in the data available. However, species’ traits are likely to influence how they respond to human pressures, and a broader geographical and taxonomic view is needed to take the next step in our understanding.

Projecting Responses of Ecological Diversity in Changing Terrestrial Systems
The PREDICTS project aims to address some of these issues by performing a meta-analysis of species responses to different human pressures, covering as broad a taxonomic and geographical data set as is available. The PREDICTS team are collecting data from published papers; however, they also hope to draw on rich datasets held by ecologists which are simply too large to have been published in full. If you are an ecologist and believe you may have data that could be used for this project, please visit the PREDICTS website to find out more. They have already collated over 800,000 biodiversity records covering more than 15,000 species. These data are being combined to form a database that will be used to answer a number of key questions about biodiversity and anthropogenic change. In particular, the PREDICTS project is interested in investigating how different taxonomic groups respond, how responses differ in different biomes and with different intensities of human pressure. They also plan to investigate how different measures of biodiversity (e.g. species richness, evenness, abundance etc) may respond differently in different species, regions and for different human pressures.

_DSC3418_watermarkBy combining data from many species and sites, across a variety of different intensities of human pressure, PREDICTS hopes to develop a deeper understanding of how different factors interact to determine species responses. From this they hope to make predictions about how biodiversity may respond to different projected future scenarios, and thus provide insights for science policy.

Turning Science into Policy
We are faced with an increasingly difficult global situation, as human populations expand, the climate changes and biodiversity declines. What makes this situation more difficult still is that we need to make decisions now and over the next few years that will impact a generation, but for which we still have insufficient data to know for sure what’s best. Making projections for climate change, human population expansions and changes in the exploitation of biodiversity is difficult. Making projections for how biodiversity will respond to those changes is even more difficult still, but it is a task we must attempt if we are to make informed decisions about the future of our planet. PREDICTS hopes to utilise what data we do have to make synthesise a more in depth and holistic understanding of how ecological communities respond to human impacts, which can be used to make predictions that will help inform science policy makers globally.

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Images copyright Lawrence Hudson and Tim Newbold, used with permission.

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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