Climate Change Turns Foliage Less Nutritious in Rainforest

Climate change affects ecosystems and species’ ability to adapt. Animals, plants and other species are already struggling with global warming and changing patterns of rainfall, facing the risk of mass extinction. A new study by senior ecologists in the US gives insights into how climate change affects biodiversity in rainforests. The study revealed that climate change has adverse impact on vegetation, where leaves become less nutritious than they used to be.

Three Decades of Expedition

In the study, Jessica Rothman, ecologist of Hunter College in New York City, and her co-authors combined several decades’ worth of data from the rainforests in Uganda.

Thomas Struhsaker, one of the authors, at Duke University in Durham, North Carolina, had initiated this research way back in 1979. He had collected mature leaves from various species of tree in Kibale National Park in Uganda and dried them in the sun. Later, he analyzed the chemical makeup of those leaves.

In 2007, Struhsaker returned to the park with a research team led by Rothman and retraced his steps. Over the next three years, the scientists studied 10 different tree species in the rainforest and examined them at least once a year. Same as before, they dried the leaves and brought them back to the lab for analysis.

During the analysis, scientists also recreated the similar work and examinations that Colin Chapman of McGill University, Canada, had done in the mid-1990s. They gathered younger leaves from eight tree species that the local red colobus monkeys like to munch on.

Study Findings

The scientists analyzed all these leaves and discovered that foliage in the forest had become less nutritious. Mature leaves of nine out of 10 tree species first studied in the 1970s now had more fiber and less protein. In the young leaves from trees used for studies in the 1990s, fiber had increased by 15% and protein had decreased by 6%.

According to researchers, these changes weren’t small. Overall, their studies suggest that nutritional quality of foliage had declined over the last 15-30 years.

But, scientists aren’t sure about the factors in the environment that are making changes in leaf chemistry.

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“Kibale rainforest has become significantly hotter and wetter over the last century. Earlier studies found that tropical trees receiving extra rainfall end up with lower nitrogen concentrations; nitrogen is a building block of protein. In forests that are facing drought, the results might be different,” explained authors.

Leaf-eating colobus monkeys are assessed as critically endangered by the ‘International Union for Conservation of Nature’. If leaves are becoming less nutritious, these forests may no longer be able to support these many monkeys.

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However, there’s certainly some good news. The monkey group hasn’t started disappearing yet, at least.

“Local monkeys are managing these changes for now. However, trees in the rainforest feed a host of other mammals, reptiles, birds, and insects. All of them are on a new food regimen they didn’t ask for. This could affect the health of the whole ecosystem,” Rothman said.

What are Rainforests?

Rainforests are very dense forests characterized by high rainfall. Rainforests get annual rainfall between 250 and 450 centimeters. There are mainly two types of rainforest: tropical and temperate. Tropical rainforests are found in Asia, Australia, South America, Central America, Africa and Mexico. They are also spotted on many of the Pacific, Caribbean, and Indian Ocean islands. Temperate forests lie between the tropics and the Polar Regions.

Rainforests accommodate around 40% to 75% of biotic species. Millions of species of plants, insects and microorganism are still believed to be identified in tropical rainforests. Tropical rainforests are known as world’s largest pharmacy — over one quarter of natural medicines have been discovered there. Rainforests generate 28% of the world's oxygen turnover.

Kibale National Park

Kibale National Park protects moist evergreen rainforest in South Uganda. The park is 766 sq km in size and contains a diverse array of landscapes. Kibale is one of the last remaining expanses to contain both lowland and highly elevated region. The park forms a continuous rainforest with 1,978 sq km. This adjoining of the parks creates a 180 km wildlife corridor, which is an important safari destination and popular for its habituated chimpanzees.