A new multi-author scientific study says that preservation of plant biodiversity provides a crucial buffer to negative effects of climate change and desertification in drylands. Preventing ecosystem degredation in a warming world is significant with drylands particularly vulnerable to environmental changes and desertification. Dryland ecosystems cover 41% of the land surface of the Earth and support 38% of the human population.
It is the first global study of its kind examining 224 dryland sites in 15 countries. The scientific paper - Plant Species Richness and Ecosystem Multifunctionality in Global Drylands (abstract) was published in the AAAS journal Science on 13 January 2012.
The study found that a site's plant species richness was directly related to its multifunctionality. Multifunctionality is the ability of an ecosystem to provide multiple services such as carbon storage, production of drinking water, food and energy, and build-up of nutrient recycling. Researchers assessed 14 functions at each site relating to the cycling and storage of carbon, nitrogen and phosphorus.
"The work involved selecting representative sites, identifying the range of plant species present, and collecting soil samples to monitor a total of 14 'functions', including soil biological activity and soil carbon levels and cycling,"said Dr Matthew Tighe, a lecturer in the School of Environmental and Rural Science at the University of New England, "All of the measures are important aspects of the system, but their combined importance is reflected in plant species richness."
"The Australian component of the project was important," Dr Tighe said, "because Australia is one of relatively few countries having large arid and semi-arid areas where agriculture is not at the subsistence level." The other countries included in the study were Argentina, Brazil, Chile, China, Ecuador, Iran, Israel, Mexico, Morocco, Peru, Spain, Tunisia, the United States and Venezuela.
Statistical analysis of the major variable factors that affect ecosystem multifuntionality found that plant biodiversity was one of the most dominant factors.
"Our findings suggest that plant species richness may be particularly important for maintaining ecosystem functions linked to carbon and nitrogen cycling, which sustain carbon sequestration and soil fertility," said co-author Professor David Eldridge, of the UNSW School of Biological, Earth and Environmental Sciences. "And because land degradation is often accompanied by the loss of soil fertility, plant species richness may also promote ecosystem resistance to desertification."
Loss of biodiversity may impair the functioning of natural ecosystems through changing the availability of drinking water, food and energy; changing the regulation of carbon sequestration and waste decomposition; and changing nutrient cycling and seed dispersal.
Dryland ecosystem temperatures are predicted to increase by climate change models. "Climate change will reduce the ability of dryland ecosystems to perform multiple functions related to the cycling of these elements. Changing climate is also likely to reduce plant richness and increase the areas affected by desertification," said Professor David Eldridge.
The study provides scientific support for ecological restoration of cleared lands rather than simplistic revegetation schemes. "If you take these findings in the context of the South West of WA, where both species diversity and endemism are very high, the threat of a changing climate is certainly a concern," said ecologist Justin Jonson from Society for Ecological Restoration Australasia. "At the same time the findings also further the case for undertaking ecological restoration of cleared lands as opposed to more simple style revegetation plantings." he told Science Network WA.
Western Australian drylands ecosystems are particularly vulnerable. Professor Glen Albrecht, Director at Murdoch's Institute for Social Sustainability remarked in an article on Science Network WA that reduced ecosystem diversity also impacts population and cultural diversity.
"With dryland ecosystems such as in the 'Wheat-Sheep' belt in WA, take out the highly diverse native vegetation and you end up with huge dryland salinity problems, soil erosion and declining fertility," he says.
"Whole sections of the wheat-belt are being depopulated, social services decline and cultural and sporting events are near impossible because there are not enough 'players'."
"Climate change not only destroys biological diversity and ecosystem services, it destroys cultural diversity and social services as well." he said. "It's time we recognised both forms of diversity as vital to the future of all life, particularly human life." concluded Professor Glen Albrecht.
- Media Release, University of New England, 13 January 2012 - International study shows drylands need 'plant species richness'
- Media Release, University of New South Wales, 13 January 2012 - Ecosystem biodiversity a key climate change buffer
- Marion Lopez, Science Network WA, 13 January 2012 - Species biodiversity buffer needed to accommodate climate change
- Fernando T. Maestre et al - Plant Species Richness and Ecosystem Multifunctionality in Global Drylands (abstract) - Science 13 January 2012: 335 (6065), 214-218. [DOI:10.1126/science.1215442]
- Image - Drylands near Hyden in the West Australian wheat belt (own photo)