Large Mammals Missing from 80 Percent of their Range due to Human Pressure

December 2007. Researchers have realised that less than 21 percent of the earth’s terrestrial surface still contains all of the large mammals it once held. The discovery highlights human impacts on biodiversity as well as the need for better protection. Results of the study are published in the latest Journal of Mammalogy. Large mammals often play critical roles within ecosystems by affecting either prey populations or the structure and species composition of vegetation. However, large mammals are highly vulnerable to human pressure. The extents of the geographic ranges of individual species have been greatly reduced because of human activities, primarily through habitat alteration and direct exploitation or persecution. Large species are particularly prone because they are hunted for the flourishing trade in wild meat, controlled as competitors, or otherwise persecuted. Severe habitat fragmentation within species ranges also results in increasingly rare intact large mammal faunas.

Comparison with 1500
The objectives of the study were to indicate where historical human impacts occurred and to show where the remaining intact large mammal assemblages are found, how they are distributed, and their level of protection. To begin, the study’s researchers compared historical (AD 1500) range maps of large mammals with their current distributions.

Results vary widely by geography. Although less than 21 percent of the earth’s terrestrial surfaces still contain the large mammal faunas that were once there, the proportions varied between 68 percent in Australasia to only 1 percent in Indomalaya. The researchers said areas that contain complete large mammal assemblages merit conservation attention because only 8 percent of that land area is well protected.
Conservation Priorities
Modern methods for designing reserves can incorporate a wide variety of data layers, and the researchers proposed that the results of their analysis be another layer to consider. Already, large international conservation organizations have used this development to prioritize their global actions. Additionally, support for long-term conservation should be directed toward intact assemblages that are small and intensively managed as well as to faunas of remote and inhospitable areas.

To read the entire study, click here.

Journal of Mammalogy is the bi-monthly journal of the American Society of Mammalogists.