BEIJING, Sept. 21 (Xinhua) -- A group of researchers have revealed the factors that drive the upward move of the world's treelines, providing new evidence for the impact of climate change on global ecosystems, according to China Science Daily on Thursday.

Mountain treelines are sensitive to climate change. However, the way that climate impacts mountain treelines is not fully understood, as they may also be affected by human activities.

A research group led by Zeng Zhenzhong from the School of Environmental Science and Engineering, China's Southern University of Science and Technology, established a global mountain treeline database by collecting high-resolution remote-sensing images of some 916,000 km of closed-loop mountain treelines across 243 mountains around the world.

The closed-loop mountain treelines encircle a mountain and are less likely to have been influenced by human activities and land usage.

After analyzing the database, the group found that temperature is the main climatic driver of treeline elevation in boreal and tropical regions, whereas precipitation is the main factor in temperate zones.

About 70 percent of closed-loop mountain treelines have moved upward, with an average shift rate of 1.2 meters per year over the first decade of the 21st century, according to the study, which was published in the journal Global Change Biology.

The study also found that treelines are shifting fastest in the tropical regions, with an average shift rate of 3.1 meters per year. For example, in Malawi, Papua New Guinea and Indonesia, some treelines are moving upward at a rate of 10 meters per year.

While the upward movement of treelines means more trees can absorb more carbon from the atmosphere and expand the habitat of some forest species, it also poses challenges for fragile ecosystems at high altitudes, according to He Xinyue, the first author of the paper.

Plants and animals at high altitudes are often very sensitive to environmental changes. As treelines moved up, they began to compete for space and nutrition, which could seriously threaten some endemic species, He added.