Eduardo CesarTug of war: when human inhabitants leave, the native vegetation reclaims the landEduardo Cesar
“That’s where my grandmother’s house was,” ecologist Camila Rezende heard someone say deep in the forest in the mountains of the state of Rio de Janeiro. Surprised that she hadn’t realized she was in an old settlement, she gradually began to discover traces of the past. “Suddenly, in the middle of the Atlantic Forest there was a lemon tree, for example, and stones that had been the foundation of a house,” says Rezende, a doctoral candidate at the Federal University of Rio de Janeiro (UFRJ) under the guidance of ecologist Fabio Scarano. The chance finding led her to investigate the spontaneous regeneration of that forest, which then covered more than a million square kilometers (km2) scattered over 17 Brazilian states, and now has been reduced to slightly under 12% of that area—mostly in forest fragments of 50 hectares or less. Reversing this situation may be key to mitigating the effects of global climate change on the human population, as reported in papers appearing in the special Atlantic Forest issue of the scientific journal Biodiversity and Conservation, published in September 2015.
Rezende assessed what has occurred between 1978 and the present in the municipality of Trajano de Moraes, a 600-km2 area in the northern Rio de Janeiro mountains. The region was occupied (and deforested) in the 18th and 19th centuries, mostly to establish coffee plantations. But after the coffee crisis triggered by the stock market crash of 1929, the plantations were abandoned and the forest gradually took back the land. In aerial and satellite photos taken in 1978, 1988, 1999, 2006 and 2014, Rezende saw that many forest areas were regenerating. The landscape, however, was far from homogeneous. “We used spatial modeling to understand why some areas were regenerating and others were not,” Rezende explains. During those 36 years, the forest cover in that area increased by more than three million hectares—a gain of 15%.
In the statistical model she developed, for each sampling unit she calculated the probability of forest regeneration under the given ecological conditions. Among the most important variables, she cites the type of relief: the rougher the terrain, the harder it is for humans to occupy and the more evident the regeneration, while flat areas continue to be occupied and used. Other important factors beyond that were solar radiation, distance from urban areas (areas closer to cities are less likely to be abandoned), soil quality and distance from forest fragments that serve as a source of seeds.
A project to restore this same area using traditional planting methods would cost an estimated $15 million. In Rezende’s view, the cost and the context of climate change make it important to adopt a new perspective on recent forests, which have been historically viewed as second-class. “Regenerating forests are increasingly valued for the environmental services they provide, such as carbon storage, water production and the associated increase in biodiversity,” she explains.
In her opinion, understanding how spontaneous regeneration works can help in planning reforestation, so that resources can be channeled to areas that really need planting. In practice, it involves lending nature a helping hand to enhance its ability to regenerate land as people leave the area. Such assistance, which would have to be evaluated on a case-by-case basis, could come in the form of creating corridors or islands of vegetation that serve as a source of seeds for regeneration, or waiting until the forest becomes established and then take steps to enrich the biodiversity.
The unknown
In any plan to expand the scale to other areas of Brazil, it may be useful to take into account the rules by which the forest operates. Some of the rules are very poorly understood, according to a study by ecologist Renato Lima of the Biosciences Institute of the University of São Paulo (IB-USP). He showed that the inventories already done in the Atlantic Forest have been limited to an area that represents 0.01% of what remains of that type of vegetation. To arrive at this estimate, Lima and colleagues compiled all the surveys done to date in the Atlantic Forest, broadly defined, which is basis for the legal definition of the forest.
Within the mosaic that constitutes this broadly-defined Atlantic Forest—which includes distinct physiognomies such as sandy restinga and the unique araucária (Brazilian pine) forest in the mountains of the state of Rio Grande do Sul, some regions have been more heavily studied than others. Little has been done in the states of Bahia or Mato Grosso do Sul. “The implications of such limited knowledge are important in decision-making about conservation,” Lima comments. “When we talk about preserving endangered species, we need to know on what knowledge such decisions are being based.”
The area inventoried for these studies was totaled up and compared to estimates from the nongovernmental organization SOS Atlantic Forest Foundation about the size of the remnants. According to the ecologist, it is not surprising that such a small percentage of the Atlantic Forest has been studied. “If we did the same thing with other biomes, we’d get a similar result; few biomes have had a large percentage sampled.”
Although it is not surprising, the estimate is alarming when viewed in the context of deforestation that continues at an estimated rate of 200,000 km2 per year, according to the 2014 report by the SOS Atlantic Forest Foundation. “The rate of deforestation is four times greater than the pace at which the remaining forests are being surveyed,” the researcher notes. “In the long term, if that situation continues, the forest will disappear before we study what little has remained.”
For this reason, Lima emphasizes the importance of directing future efforts towards the lesser-known areas, in addition to reducing deforestation. He also reports that the federal government is encouraging states to conduct forest inventories. Santa Catarina has already done its part, sampling 60% of the known Atlantic Forest area within that state. The problem, says the researcher, is that the methodology used for the National Forest Inventory differs slightly from the one used in the other completed studies. For example, it includes trees with a trunk diameter of at least 10 centimeters at chest height. “This makes sense for the Amazon, but studies in the Atlantic Forest involve young trees and include diameters starting at five centimeters,” he explains. “It’s going to be hard to consolidate the new data with the existing ones.”
To streamline the studies and save resources, Lima has partnered with Alexandre Adalardo and Paulo Inácio Prado, professors at IB-USP, to coordinate a collaborative online database that will aggregate Brazil’s forest inventories and be available for use by the scientific community. The project, called TreeCo (Neotropical Tree Communities Database), is a natural extension of the Atlantic Forest assessment and already has data on two million trees.
Eduardo CesarPalm hearts crop competes for space with forest in Vale do Ribeira, in the countryside of São Paulo StateEduardo Cesar
The future
Lima’s work is not just a case of romanticism on the part of a lover of flora, fauna and the network of interconnections between them. “The most endangered species may be our own,” cautions Fabio Scarano of the Brazilian Foundation for Sustainable Development (FBDS) and UFRJ. The Atlantic Forest domain is home to more than 100 million Brazilians and the locus of the country’s economic engine. Even though 90% of the people living within the biome are concentrated in urban centers like São Paulo and Rio de Janeiro, more than half the country’s agricultural land is also found within its boundaries. In a review article, Scarano and Paula Ceotto of the NGO Conservation International examined the effects of local climate and land-use changes on the forest and on the human population. “Environments that have lost much of their ability to support living systems are much more vulnerable,” Scarano says. “And poor people are even more vulnerable.”
Scarano, who is among the group of authors on the Intergovernmental Panel on Climate Change (IPCC), believes that there is still a need for many more studies of future scenarios. “Expectations are that species will migrate southward as the temperature rises, but the problem is that there are already people living in that area, and there’s not much space left,” he cautions.
Nevertheless, he is optimistic about the possibility of ecosystem-based adaptation, which includes payment for environmental services, restoration of the forest and expansion of protected areas. To that end, Scarano advocates increasing collaboration among researchers, decisionmakers, public policymakers and the people, who must be informed and convinced about what needs to change for the benefit of all. “Optimizing resources and taking care of the ecosystem means generating revenue through tourism, more productive farming and the discovery of potential drugs, for example.”
Scarano’s optimistic view is based on the natural resilience of the forest, as was shown in Rezende’s study, and on the idea that human interests are compatible with nature conservation. In his view, Brazil has a responsibility to take that step and use the ecosystems as part of the solution to the impact of global warming on social well-being. But it needs to be taken faster than in the past. “We have until 2030; if by that time we haven’t changed our patterns of consumption and use of the land, we’re likely to get to 2050 with a 2º Celsius temperature rise, with harmful effects on life as we know it,” he cautions. Much depends on the outcome of the Paris Climate Conference (COP21) in December 2015. “If the goals proposed by the Brazilian government are achieved, we are 15 years away from an environmental paradise,” the researcher comments exaggeratedly.
Project
The role of functional diversity in structuring tropical tree communities: A model-based approach (nº 13/08722-5); Grant Mechanism Scholarships in Brazil – Regular – Postdoctoral; Principal Investigator Paulo Inácio Prado (IB-USP); Grant Recipient Renato Augusto Ferreira de Lima (IB-USP); Investment R$ 131,224.64.
Scientific articles
LIMA, R. A. F. de, et al. How much do we know about the endangered Atlantic Forest? Reviewing nearly 70 years of information on tree community surveys. Biodiversity and Conservation. V. 24, No. 9, p. 2135-48. September 2015.
REZENDE, C. L. de, et al. Atlantic Forest spontaneous regeneration at landscape scale. Biodiversity and Conservation. V. 24, No. 9, p. 2255-72. September 2015.
SCARANO, F. R. & CEOTTO, P. Brazilian Atlantic Forest: Impact, vulnerability, and adaptation to climate change. Biodiversity and Conservation. V. 24, No. 9, p. 2319-31. September 2015.
