The map adds together influences from population density, access from roads and waterways, electrical power infrastructure, and land transformation such as urbanization and agricultural use. It reveals that 83 percent of the land's surface is under human influence, while a staggering 98 percent of the area where it is possible to grow rice, wheat or maize is directly influenced by human beings. At the same time, wide swaths of land still remain wild, including: the northern forests of Alaska, Canada and Russia; the high plateaus of Tibet and Mongolia; and much of the Amazon River Basin.
According to WCS and CIESIN, wild areas can still be found in all the ecosystems on the land's surface, though some on a much smaller scale. Called the "last of the wild," the authors look at these less-influenced areas as opportunities for conservation of wild places all over the world.
"The map of the human footprint is a clear-eyed view of our influence on the Earth. It provides a way to find opportunities to save wildlife and wild lands in pristine areas, and also to understand how conservation in wilderness, countryside, suburbs, and cities are all related," said the paper's lead author Dr. Eric Sanderson, a landscape ecologist with WCS. "The map should be looked at as a blueprint for individuals, institutions and governments to understand our current influence on the planet and figure out ways to lessen the negative impacts, while enhancing the positive ways that people interact with the environment."
The authors of the study also gave numerical scores to various areas around the world; the lower the number, the lesser the degree of human influence. Many of the world's largest cities, including New York, Beijing, Calcutta, etc. received the highest scores. But the authors of the study say that even among areas under heavier human influence, there are still opportunities for wildlife, pointing to examples like the progress made in restoring the Hudson River, and in India, where tigers share their landscape with one billion people.
"This map can be used to set specific targets for action," according to data specialist Marc Levy of CIESIN. "What can't be measured can't be managed--with this map we have an important management tool, a basis for scientific measurement of anthropogenic influences on nature."
"The two lessons of the human footprint are this: we need to conserve the last of the wild, because they are places where all the parts of nature are more likely to remain, and where conflicts with human infrastructure are least; and we need to transform the human footprint, so nature can still be nurtured everywhere, including in more heavily influenced areas. We can do both and nature is often resilient, if given half a chance," said Sanderson.
This study also vividly illustrates the application of geographic information systems (GIS) technology as a way of integrating diverse geographic data to reveal new patterns in a persuasive way. This work was only possible because of increased access to global datasets on roads, land use, and human population density in recent years.
This work was supported by grants from the Prospect Hill Foundation, the Center for Environmental Research and Conservation (CERC) at Columbia University, and in-kind support from the ESRI Conservation Program.