August 17, 2005
New Global Bird Map Suggests ‘Hotspots’ not a Simple Key to Conservation
The first full map of where the world's birds live reveals their diversity 'hotspots' and will help to focus conservation efforts, according to research published in Nature today (18 August).
The findings are drawn from the most complete and detailed picture of bird diversity yet made, based on a new global database of all living bird species.
The map also shows that the pattern of bird diversity is much more complicated than previously thought.
The researchers conclude that different types of 'hotspot' - the most bird-rich locations on the planet -- do not share the same geographic distribution, a finding with deep implications in both ecology and conservation.
For birds, hotspots of species richness are the mountains of South America and Africa, whereas hotspots of extinction risk are on the islands of Madagascar, New Zealand and the Philippines.
"In the past people thought that all types of biodiversity showed the same sort of pattern, but that was based on small-scale analyses," says senior author Professor Ian Owens of Imperial College London. "Our new global analyses show that different sorts of diversity occur in very different places."
Biodiversity hotspots have a high profile in conservation, but are controversial as their underlying assumptions remain untested. The key assumption is that areas 'hot' for one aspect of diversity will also be hot for other aspects.
Their analyses now show that surprisingly, this is not the case - different types of hotspot are in fact located in different areas.
"Different types of diversity don't map in the same way," Prof Owens says. "There is no single explanation for the patterns. Different mechanisms are therefore responsible for different aspects of biodiversity, and this points to the need to base conservation strategy on the use of more than one measure of biodiversity."
The team mapped three different measures of diversity for the study: species richness, threatened species richness (as assessed by their extinction risk), and endemic species richness (birds with a small breeding range). Only the Andes in South America contains bird hotspots under all three measures.
To understand the mechanisms behind large scale biodiversity patterns, the researchers first had to construct global maps before delving into them.
"The prior bits of work were horribly dispersed: in paper maps on expert's desks, or in very old books and the heads of aging experts who had originally surveyed the areas," said Professor Owens.
It took five person years to get the data into a digital mapping format known as a 'GIS system'. This database was then used to score the presence or absence of each of the nearly 10,000 different bird species in a grid covering the world's land area. Each of the 20,000 cells in the grid is 100 km squared and contains an area similar to that of Cyprus.
"We hope that birds are a model for this type of work," said Professor Owens. "There is such a wealth of historical information about them. They are also large, colourful and you can see them in the day time. It's very difficult to do at this scale for other organisms."
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