Geographic distribution of Atlantic Rainforest trees could decrease 65% by 2100

Brazilian researcher presents estimate based on the worst case scenario for global warming at recent conference.

By Noêmia Lopes

Agência FAPESP – If the most optimistic projections of the Intergovernmental Panel on Climate Change (IPCC) come true and the temperature in the areas with remnants of the Atlantic Rainforest increases by up to 2 degrees Celsius, the geographic distribution of trees in this forest could show a 30% reduction by 2100. If, however, the IPCC’s worst-case scenario were to occur and global warming reaches 4 degrees Celsius, the reduction could reach 65%.

This alarm was sounded by Carlos Joly, coordinator of the Research Program for Characterization, Conservation and Sustainable Use of Biodiversity in São Paulo State (BIOTA-FAPESP) and research at Universidade Estadual de Campinas’s Biology Institute (IB/Unicamp), during the sixth meeting in the 2013 BIOTA Education Conference Cycle, held on July 22 at FAPESP in São Paulo.

The numbers were obtained from a survey that began in herbaria. “We identified at least 30 points of exact occurrence of trees in the Atlantic Rainforest. With this information, we mapped where they are found today under certain temperature conditions, precipitation, soil types and altitude,” explained Joly.

Given the 30 initial points, the next step was to use an algorithm to identify the places where a given species could potentially occur. This additional information was the basis of a second map. According to Joly, “this allows us to say that a given species is capable of occurring in certain locations under certain annual temperature and precipitation conditions.”

The IPCC projections then allowed the scientists to outline the scenario in 2100, considering the best- and worse-case scenarios. “We estimated that the northeastern portion of the remaining forests – where rainfall is projected to decline significantly – will diminish. And the geographic distribution of the species will be more restricted to areas like the Serra do Mar mountain range, where precipitation is guaranteed and the landscape prevents the temperature from rising too much,” affirmed Joly.

Carbon stocks

Another subject covered during the conference was the monitoring of carbon stocks in São Paulo’s Atlantic Rainforest in a stretch equivalent to 14 football fields between Ubatuba and São Luiz do Paraitinga.

Since 2005, studies conducted under the auspices of BIOTA-FAPESP and the FAPESP Program for Global Climate Change Research (PFPMCG) have investigated the remnants of the Atlantic Rainforest region, including gas exchange between plants and the environment.

The surveillance is conducted with steel belts placed on tree trunks. Measurements of the diameter every two years indicate how much carbon fixation is occurring. “We also monitor trees that die and begin decomposition and new plants that grew enough in the preceding period to enter this sample,” affirmed Joly. A 60-meter tower, equipped with a large set of sensors, also measures the gas flow exchange, in addition to other factors including radiation, rain and wind.

The results obtained to date indicate the existence of large carbon stocks, primarily in the soil of higher regions, where cold temperatures hinder decomposition and where there is an accumulation of litterfall – the fluffy layer formed from fallen leaves on the ground.

“We hypothesize that in the heating process, the litterfall that has accumulated for thousands of years will decompose more quickly. In that case, the litterfall will become a carbon source, and we will lose the environmental storage service that these species offer,” explained Joly.

In the coming years, in partnership with British researchers, monitoring in the Atlantic Rainforest will be compared with studies in the Amazon Forest and forests of Malaysia. We already know, for example, that, unlike the Atlantic Forest, the Amazon Forest does not accumulate carbon in the soil. Annual measurements show that the Amazon Forest establishes exchanges with the environment that result in a near-zero balance.

Fauna and sensing

André Victor Lucci Freitas, a researcher at IB/Unicamp, also participated in the conference, presenting data on the origin, evolution and diversity of the fauna of the Atlantic Rainforest. He indicated that the forest’s broad diversity and high fauna endemism can be explained by a set of processes.

“The interaction between the environmental tolerances of different groups of animals, the heterogeneity of habitats and the historical processes (like climate variations in the past) explain the high diversity found throughout the Atlantic Rainforest,” said Freitas.

The third speaker, Flávio Jorge Ponzoni, a researcher at the National Institute for Space Research (INPE), addressed the behind-the-scenes aspects of developing an atlas.

“Surveillance of the remnants of the Atlantic Rainforest, which is now conducted annually, is based on the interpretation of satellite images. Aerial photographs result in greater detail, but this is still a very expensive technique for the large areas that we need to monitor,” he said. Another challenge is identifying smaller areas of deforestation caused by urban expansion.