World's Forests Show Trend of Growing on Inclined Land

A survey of the world's forests has revealed that after generations of trees being cleared from low-lying lands by humans, there is now a worldwide trend of forests growing up-hill, particularly in the most developed countries.

Writing in the journal Nature Communications, researchers from Aarhus University in Denmark present evidence of a clear correlation between forests growing an incline in countries with the most economic prosperity and political stability.

"The better the economy, the better the political organization, and the more orderly societal conditions a country has, the more efficient the population has been at restricting forests to steep areas, reflecting their lower utility and value," the researchers said in a statement from Aarhus University.

The research team used high-resolution satellite data to analyze global tree cover between the years 2000 and 2005, and plotting the data with regard to terrain, climate, human activity and a variety of socioeconomic and political factors.

Systematic reduction of forests on low-lying land has been a condition in developed countries for a long time, but the researchers found the trend has also accelerated recently in less-developed countries.

The researchers contend that as populations grow and human impacts increase, the large, unspoilt stretches of forest like those seen in the Amazon, Siberia and the Congo will also be affected.

"The more well-developed societies around the world are now increasingly replanting trees, just as forests are naturally regrowing in areas that have been abandoned as people move to the cities," the researchers said. "These dynamics occur in steep areas in particular, given modern efficient land use practices cannot easily be implemented here, strengthening the development leading towards future forests becoming concentrated on slopes."

Brody Sandel, one of the study's authors, said a trend of inclined forests leads to concerns about biodiversity in the future.

"The remaining forests on slopes are typically divided into smaller areas that are not continuous. For example, fragmentation reduces the availability of interior forest habitat that is preferred by many bird species. There are also a number of large predators, such as big cats like the tiger, which require extensive areas of continuous forest to be able to get enough food or avoid human persecution," Sandel said.

However, a trend toward sloping forests may not be entirely bad news, said Jens-Christian Svenning, a professor Aarhus University who led the research.

"On the other hand, species in steep mountainous areas can better track their preferred climate as it becomes warmer. Hence, considering future climate change, it's fortunate that forests will especially occur on steep terrain in the future. It's thus a blessing in disguise that the general loss of forests has less effect on slopes," he said.