Persistent Drought 'Browning' Africa's Congo Rainforest

Africa's Congo rainforest is browning, a new study based on data from NASA satellite has found.

The study, conducted by Liming Zhou of University at Albany and colleagues shows that between 2000 and 2012, forest cover in Congo has become brown. The research shows that the forest is adjusting to long-term drying trends.

The forest in Congo is the second-largest rainforest. Since 2000, the region has witnessed a persistent drought. The continuous dry spell could lead to changes in tree composition in the area.

Some 10,000 species of tropical plants grow in the Congo Basin and as much as 30 percent are unique to the forest. The region is also home to chimpanzees, bonobos, gorillas and elephants. Altogether some 1000 species of birds, 400 species of mammals and around 700 species of fish live in the Congo Basin, according to the World Wildlife Fund.

The decline in forest cover would not only lead to habitat loss of several species of animals and birds, but also cause dramatic changes in carbon storage.

For the study, researchers used Enhanced Vegetation Index to see whether or not there was a change in greenness of the forest cover in Congo. The greenness is a reliable indicator of the health of the forest, according to the researchers.

The team found that there is a steady trend in forest decline in the region. The rainforest canopy is slowly "browning." According to the researchers, the response of Congo forest to long-term drought is different from Amazon rainforests where episodic dry events result in trees dying quickly.

"Forests of the Congo Basin are known to be resilient to moderate climate change because they have been exposed to dry conditions in the past few hundred years," Sassan Saatchi of Jet Propulsion Lab, co-author of the study, said in a news release. "However, the recent climate anomalies as a result of climate change and warming of the Atlantic Ocean have created severe droughts in the tropics, causing major impacts on forests."

The browning of forest canopy is consistent with the decreases seen in water levels in the region. Also, temperature in the Congo is rising and trees are being exposed to more sunlight than before due to loss of could cover. During other times, extra sunlight would mean more photosynthesis. However, now the extra sun exposure has become a major stressor for the trees.

In the next part of the study, researchers would be looking at the effects of climate change on individual tree species. The dry spell might favor deciduous trees over evergreen trees.

"It's important to understand these changes because most climate models predict tropical forests may be under stress due to increasing severe water shortages in a warmer and drier 21st century climate," Zhou said.

The study is published in the journal Nature.