Warming world threatens plant diversity

By Heather Catchpole 29 March 2010
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The botanical riches of countries including Australia could be hit hard as temperatures rise, a new study warns.

THE BOTANICAL RICHES OF countries including Australia could be hit hard as temperatures rise, a new study warns.

Tropical nations, which are least responsible for greenhouse gas emissions, may see the biggest drop in their capacity to maintain diversity in response to climate change, report German and US scientists behind the study.

“Due to expected dryer conditions in future, the habitat suitability for many Australian plants may decrease in many parts of the continent, possibly leading to a considerable reduction of their range sizes,” says lead author Jan Henning Sommer.

“Climate change could bring great confusion to the existing pattern of plant diversity, with scarcely predictable consequences for our ecosystems and mankind,” says Jan, who is based at Bonn University’s Nees Institute for Biodiversity of Plants.

Great confusion

The research, published in the latest edition of the British journal the Proceedings of the Royal Society B, looks at current plant species richness in various world regions and their relationship with the changing climate.

In Australia – which has one of the highest levels of greenhouse gas emissions per person of any nation – the future climate may not sustain the present number of plant species, the report says. The research considered the capacity of a region to house a certain number of species and how this may shift, Sommer told Australian Geographic.

The team used computers to model this ‘capacity for species richness’ on a global scale with a resolution of 110 x 110 km. They then ran 18 climate scenarios for each region developed by the UN’s Intergovernmental Panel on Climate Change (IPCC) for the year 2100.

These scenarios cover an expected rise of between 1.8ºC and 4ºC compared to temperatures prior to the industrial revolution, with the greater rise representing a ‘business as usual’ scenario if there are no great cuts in global greenhouse gas emissions.

Most extreme scenario

A low temperature rise would see species richness shift regionally, but remain constant in terms of the global average, the study found. However, cool and moist regions, which mostly coincide with industrialised nations, are more likely to benefit, while sub-tropical and tropical areas will experience greater biodiversity loss.
But larger-scale temperature rises — over 2ºC, which many experts now think is the most likely scenario — shifts the balance to an overall global drop in diversity.

According to Lesley Hughes, a climate change ecologist at Macquarie University in Sydney, these greater rises in temperature are where we are most likely headed. “We are now travelling along the most extreme of the IPCC scenarios in terms of greenhouse gas emissions. This means that the worst case scenarios… are likely to be closest to reality.”

Because Australia is very flat there is little opportunity for plants to move uphill to track cooler climates, she adds. “Even those species that have effective means of dispersal and can thus keep up with shifting climate zones, the high level of habitat fragmentation means that many will be unable to find suitable habitat to move into.”

Read more of our articles on Australian plantlife.