Scientists From Syracuse University And The Netherlands Create First Global Map Of Grazing Mammal Biodiversity

“We developed a way to identify prime regions for mammal diversity that could potentially become areas for conservation or restoration,” says Mark Ritchie, professor of biology in Syracuse University’s College of Arts and Sciences. Ritchie worked on the study with Han Olff and Herbert H.T. Prins of the Wageningen University. “We were able to predict and explain the number of species in a given area based on the amount of rainfall and the fertility of the soil.”

The global map that resulted from their research shows that more than half of the areas that are prime regions for a diverse array of plant-eating mammals has already been converted to agriculture and has lost its diversity. Another 25 percent of the prime regions may be converted to agriculture over the next 25 years. The researchers predict that by 2025, less than 1.2 percent of the earth’s surface may remain to support uniquely diverse grazing ecosystems.

“We are concerned that these prime regions show very little overlap with areas designated as ‘hotspots’ for the biodiversity of plants, birds, reptiles and other types of mammals, “ Ritchie says. “Thus, the areas we have identified for plant-eating mammals would have to be conserved separately.”

Large plant-eating mammals, such as bison, antelope, giraffes, hippos and elephants are among the most visible and important wildlife species, Ritchie says. However, the factors that control their biodiversity, or number of species in an area, have not been fully understood.

Contrary to popular belief, areas of high rainfall do not have the most diverse populations of plant-eating mammals, Ritchie says. While the areas tend to produce lots of vegetation, the vegetation does not contain enough nutrients to support smaller species, such as rabbits and hares. Likewise, dry areas do not produce enough total vegetation to support larger species, such as caribou, giraffes, buffalo and elephants.

The most diverse populations of plant-eating mammals are found in areas of moderate rainfall, such as the Serengeti plains in Africa, Yellowstone National Park in the United States and the Punjab region of India, Ritchie says. “The areas tend to produce enough vegetation to support large mammals, and vegetation that is of high enough quality to support small mammals. That is especially true in areas where the soil is most fertile,” he says.

Ritchie, Olff and Prins are the first to develop a model that could accurately predict the places that would support the most diverse array of plant-eating mammals. They tested their model by gathering data on mammalian populations in 34 sites in North America and 85 sites in Africa. For each site, they calculated the amount of plant-available moisture and nutrients and compared those results with the number and types of species in the test sites.

“Some regions, such as the northern Great Plains in North America, may be highly suitable for restoration of large herbivore diversity if agriculture was abandoned,” the authors write in the paper. “Our approach is powerful because it identifies how plant resources constrain the distribution of different-sized herbivores. We use this relationship to predict global-scale patterns in large herbivore diversity. Similar approaches could be applied to other groups of organisms to help identify critical areas for current conservation and future restoration of biodiversity.”

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