Friday, January 6, 2012

Climate change and habitat loss threaten biodiversity, extinction rate underestimated

Two new scientific papers have emphasised the threat to biodiversity from the impacts of climate change and habitat loss. A study by US ecologist Mark Urban identified that predictions of the loss of animal and plant diversity due to climate change may be greatly underestimated as most predictions of the rate of extinctions don't take into account species competition and movement. A second key global study by University of Queensland and Australian CSIRO scientists emphasised the link between current climate, climate change and habitat loss on plants and animals on a global scale.

Multiple processes are driving the global loss in biodiversity and understanding the synergistic effects on animal and plant populations will be important for wildlife conservation efforts this century.


Species are already moving in response to climate change. Recent research on the velocity of climate change has estimated the average movement of climate envelopes at 27.3 km/decade on land, and 21.7 km/decade in the ocean.

Perhaps the most cost effective long term way to slow species extinctions and biodiversity loss would be to take immediate action in mitigating climate change by reducing CO2 emissions. This may stabilise habitats sometime in the future. If all the countries carried out their voluntary emissions reduction commitments, the world is heading for 3.5C temperatures rise by 2100. At business as usual rates of emissions we are headed for 6C by the turn of the century according to Fatih Birol, the International Energy Agency's chief economist. Both of these are disastrous scenarios for species biodiversity and extinction rates.


Immediate action to halt deforestation, logging of native forests and forest degradation in the first world and third world would slow carbon emissions and retain valuable carbon sinks as well as preserving valuable habitat for species under stress from climate impacts.

But with the global population still increasing and expected to grow by 2.5 billion people by 2050, pressure will be placed on maximising food production and agriculture which will impact further habitat loss. Martine Maron, a lecturer inEnvironmental Management at University of Queensland asks Food vs. fauna: can we have our biodiversity and eat, too?


Extinction rates underestimated - the importance of species competition and dispersal rates

"We have really sophisticated meteorological models for predicting climate change," says ecologist Mark Urban, the study's lead author. "But in real life, animals move around, they compete, they parasitize each other and they eat each other. The majority of our predictions don't include these important interactions."

Each species has a different dispersal rate. Some species may not be able to move fast enough, or high enough if there are mountains available, to keep up with their climate envelope and are likely to die off. And when a species does manage to find suitable habitat, they may be outcompeted by the species already there or the one who arrived there before them.


The study - On a collision course: competition and dispersal differences create no-analogue communities and cause extinctions during climate change (abstract and full paper) - by Professor Mark Urban, an ecologist at the University of Conneticut, and biologists Josh J. Tewksbury and Kimberly S. Sheldon from the University of Washington, was published in the the Proceedings of the Royal Society B: Biological Sciences.

The authors developed a complex mathematical model that takes into account the varying rates of migration and the different intensities of competition seen in ecological communities, with a view to predicting how successful species will be at shifting to new habitats.

Animals and plants that can adjust to climate change, according to their model, will have a competitive advantage over those that don't. The climate change losers will be animals with small geographic ranges, specific habitat needs and difficulty dispersing. These animals are also more likely to be overrun by other species that can tolerate a wider range of habitats.

Through the modelling the authors show that both interspecies competition and dispersal variation as factors acting singly and together dramatically elevate extinction risks due to climate change.

We show that interspecific competition and dispersal variation, both alone and together, dramatically alter community responses to climate change by elevating extinction risks, altering diversity patterns and creating no-analogue communities. Competition affects community responses to climate change through three inter-related mechanisms:
  1. decreasing population abundances, which increase extinction risk and slow climate tracking;
  2. preventing species from colonizing newly available environments; and
  3. causing the extinction of species that would otherwise persist owing to their broad thermal performance profiles.

"When a species has a small range, it's more likely to be outcompeted by others," Urban says. "It's not about how fast you can move, but how fast you move relative to your competitors."

Mark Urban identified tropical communities as being particularly vulnerable due to many species living in small areas.

The study concludes with a warning to organisations tracking biodiversity of the danger of underestimating climate impacts and a suggestion as to which species to concentrate protection efforts on.

...Because species interact and differ in dispersal ability, we might be vastly underestimating climate change impacts on biodiversity. This means that current predictions underlying biodiversity threats used by governments and conservation organizations could be conservative. We challenge ecologists to incorporate species interactions and dispersal differences into future predictions of biodiversity under climate change, and we suggest that conservation biologists should consider concentrating protection efforts on those species that disperse poorly and interact strongly.

Biodiversity impacted by global warming, land use change, and severe habitat loss

A related study from the University of Queensland and CSIRO scientists measured the relationship between current climate, climate change and habitat loss on plants and animals on a global scale. The study found that areas with high temperatures and where average rainfall has decreased over time increase the chance of a species being negatively affected by habitat loss and fragmentation.

"Human population growth has caused significant habitat degradation across the globe, typically in support of agriculture and urban development," lead researcher Chrystal Mantyka-Pringle from UQ's School of Geography, Planning and Environmental Management said.

"This alone has negatively impacted many species, but combined with rises in temperature and reduced rainfall as a result of a changing climate, there could be catastrophic results for some populations. Serious declines are already a reality for many species."

Like the study by ecologist mark Urban, the researchers emphasis that habitat loss has important implications for the conservation of biodiversity under climate change. "Conservation policy and management strategies that don't take into account the combined effects of habitat loss and a changing climate may be inefficient and at worst ineffective," Ms Mantyka-Pringle said.

"In areas where the effects of climate change and its interactions with habitat loss are expected to be severe, our current management approaches may be inadequate," she said. "In these cases more proactive management strategies such as moving species, engineering habitat, and even abandoning our efforts to save certain species in one area in favour of other areas may be more effective."

In the article abstract the authors say

Climate change and habitat loss are both key threatening processes driving the global loss in biodiversity. Yet little is known about their synergistic effects on biological populations due to the complexity underlying both processes. If the combined effects of habitat loss and climate change are greater than the effects of each threat individually, current conservation management strategies may be inefficient and at worst ineffective. Therefore, there is a pressing need to identify whether interacting effects between climate change and habitat loss exist and, if so, quantify the magnitude of their impact...

The study found that current maximum temperature was the most important determinant of habitat loss and fragmentation effects, with mean precipitation change of secondary importance. The authors argue it is becoming increasingly apparent that ecosystems and species are not at risk from a single threat but rather a multitude of factors.

"Understanding the synergistic effects between climate change and other threatening processes has critical implications for our ability to support and incorporate climate change adaptation measures into policy development and management response," Ms Mantyka-Pringle said.

Both of these papers stress different aspects of the impact of climate change on biodiversity. Multiple factors such as habitat loss, warming temperatures, changing rainfall patterns, species competition and varying dispersal rates will drive many species to extinction this century.

Without effective climate mitigation and land use regulation, conservation efforts will be costly and will need to be targeted to particular habitats and species. There will be many difficult decisions about what species to attempt to save and how best to do it. But for many species that we share this earth with, it will certainly be too little too late.

Sources:

  • Eurekalert Media Release, January 3, 2012 - Climate change models may underestimate extinctions
  • Mark Urban, Josh J. Tewksbury and Kimberly S. Sheldon - Proceedings of the Royal Society B: Biological Sciences, January 4, 2012 - On a collision course: competition and dispersal differences create no-analogue communities and cause extinctions during climate change (abstract and full paper)
  • University of Queensland News, January 5, 2012 - World-first global study links climate to severe habitat loss
  • Chrystal S. Mantyka-pringle, Tara G. Martin, Jonathan R. Rhodes, Global Change Biology - Interactions between climate and habitat loss effects on biodiversity: a systematic review and meta-analysis (abstract)
  • Image from University of Queensland News - Caption: The magnitude of habitat loss/fragmentation effects were greatest in regions with high maximum temperatures