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Fire against fire

Controlled burning in the Amazon seeks to understand impact on fauna and flora

from Querência*

It is 9:30 on the morning of August 16, and the sun that blazes over Fazenda Tanguro, in Querência, in the east of Mato Grosso, is heating the heads of three dozen people on the road between the pasture and the forest. For those scientists, firemen, students, farmers and field technicians infested with ticks, though, the rule in force was the hotter the better: they are there to set fire to the forest and to start a paradoxical scientific experiment. In order to understand how fires typical of the region threaten the transition forest between the Cerrado (savanna) and the Amazon Forest, they are going to cause one more – but with method.

The burning is half an hour late, but nobody seems to worry. It is going to last three days, in successive lines of fire, in this first area of 100 hectares (ha). In the following years, the scientific fire will incinerate another to 100 ha plots, adding up to 300 ha, which will be compared with another 150 hectares, divided into three control plots. In the course of six years, a census will be taken of fauna and flora, to understand better how the forest reacts or succumbs to seasonal fire, and is converted into a savanna more in the style of the Cerrado.

The transition forest to which this state from the Center-West owes its name is the piece of the Official Amazon most threatened by hidden deforestation, which does not appear clearly in the satellite monitoring system for remaining hidden under the crowns of the trees, as was shown by a study of the Environmental Research Institute of Amazonia (Ipam), published in 1999 in Nature. In the year of 1998 alone, when the drought from an El Niño filled the forests with shriveled up leaves and branches, the estimate is that 40,000 square kilometers (km²) of standing forest, much of it transition forest, fell victim to bushfires, usually accidental.

At the current pace, by 2050, only 15% of this biome would be left over, according to a model developed by Ipam and by the Federal University of Minas Gerais (UFMG). The pyrotechnic season at Fazendo Tanguro was baptized as a Savannization Experiment. It is yet one more idea from Ipam, which had already covered one entire hectare of the Amazon Forest with plastic panels, to simulate a drought in the El Niño style, in the Tapajós National Forest, near to Santarém, in Pará. This time, the area of this nongovernmental research organization is inside a farm of the André Maggi group, of the family of Blairo Maggi, the “soybean king” who became governor of the State of Mato Grosso. They set off from the concept that what drives 80% of deforestation today is the predatory and illegal extraction of timber, combined with cattle raising. Soybeans may contribute more indirectly, to the extent that the conversion of pastures into mechanized crops enhances the land and stimulates the opening up of new areas further on.

Tanguro covers almost 82,000 ha, equivalent to a rectangle of 10 km by 82 km. About 35,000 ha had already been deforested for cattle raising by the previous owners, two banks, Santander and Noroeste. The areas defined as being for permanent preservation, such as those adjacent to watercourses, add up to 3,132 ha. The farm also has an area of legal reserve of 46,569 ha, over half of the total. With the progressive conversion of pasture into crops, at the end of this year the planting of soybeans at Tanguro should reach 25,000 ha, an investment of R$ 44 million.

Besides planting, the group buys soybeans from another 500 producers, under the pre-financing system, which puts it in a privileged position to encourage them to adopt healthy environmental practices in production. It is this potential for advancing the idea of sustainability that Ipam has its eyes on. There is three times more land (something like 600,000 km²) in private legal reserves than in conservation units like national parks and forests.

When it all seems to be ready and the teams of igniters and measures in position, the fire begins on two fronts of a thousand meters (m), separated by 500 m, which advance into the forest at right angles to the road that skirts the pasture. The scene in the forest has something surreal about it, and not only for the fire that leaves everyone’s pants scorching. “It’s great fun”, says, amongst laughs, the scientific coordinator of the experiment, Daniel Nepstad, an ecologist from Ipam. At his side, fireman Abadio José Cunha Jr., or Major Cunha, proposes the use of a gas blowtorch, but the scientist comes out in defense of kerosene, which would make a more sustainable flame. At Tanguro, all they talk about is the “burning for the good”.

The burning crawls at 10 m/h, half the speed originally forecast. But in the afternoon, the flames take heart. In a clearing, where the sunlight has shriveled up the material on the ground, they produce a deafening noise, coming from flames of 10 or 20 meters in height – it is difficult to assess this, at a prudent distance of 30 m. But the flames measured by teams of two students usually settle down in the region of 5 to 10 centimeters. It is an attempt to look for reliable information about how, under constant stress from fire, the transition forest threatened by savannization behaves. In Brazil, the most common savanna is the Cerrado, which flanks the Amazon Forest on the southern and eastern sides. Tanguro’s boundaries are only 20 km from the Cerrado and another 20 km from the Xingu National Park.

“With what frequency of fires does the forest cease to be a forest?” This is the main question to be answered by the experiment, according to Nepstad. He is one of the coordinators of the project for Ipam, along with biologist Claudia Azevedo-Ramos, besides a fixed team that takes in another five institutions: the Federal University of Pará and the University of Brasilia, on the Brazilian side, plus the Woods Hole Research Center and Yale and Stanford Universities, from the United States.

The flames from unintentional fires, usually caused by sparks from neighboring agricultural areas, run over the forest floor at a slow pace, 10m/h to 20 m/h. They leave behind trees with fewer leaves, which fall to the ground and become drier, under the action of the larger quantity of sunlight that penetrates through the thinned-out canopy. With global climatic change, El Niños may occur with greater frequency, speeding up the vicious circle of parching and inflammability of the transition forest.

Brazil the exporter
With the vigor of the agricultural front, time and time again resorting to fire to manage pastures and open up new areas for farming, the result is an inevitable pressure on the transition forest and a giddy increase in the risk of savannization. A stronger and more important factor is the very capitalization and profitability of agriculture and cattle raising. Soybeans and beef command increasingly higher prices on the international market. Brazil is now emerging as the main exporter of these commodities – which makes agribusiness a crucial source of hard currency to fuel the servicing of the foreign debt. According to an estimate from the United States Department of Agriculture, there are 150 million hectares (1.5 million km²) of land with a potential for mechanized farming in Brazil. One of the largest regions with a profile for the expansion of soybeans in precisely in Mato Grosso, according to a study by Maria del Carmen Vera Diaz, from Ipam. “It’s the biggest environmental issue of the decade”,says Nepstad.

In the path of the cattle and the soybeans, though, lies the transition forest, which shares with the denser Amazon Forest a major part of its biodiversity. Biologist Oswaldo de Carvalho Júnior, from Ipam, says that 65% of the 46 species of mammals that the textbooks say should occur in the region have now been observed in the area of the experiment. Even a bush dog (Speothos venaticus), which ought to live further south, has been sighted.

Carvalho Jr. is responsible for the experiment’s fauna module, along with Lisa Curran, from Yale, who just on the first day saw a band of six monkeys. One of the objectives of the experiment is precisely to discover which are the animals most affected by the repetition of bushfires. Animals disperse seeds or feed on them, which means that the composition and the density of the post-fire fauna will influence the profile of the forest. On the other hand, it is not even known for sure which are the trees that suffer most. For scientists, it is not enough to know that the most vulnerable ones will be those with thin bark, this has to be detailed with a lot of data.

Out another way, it is not enough to set fire to the forest – there has to be a lot of instrumentation. That is why the researchers took a month to prepare the experiment. Without the equipment and the method, it would be a burning like any other. But there has never been a burning like this one, beginning with the cost, US$ 110,000 a year. Temperature and relative humidity of the air are the most important measurements. They are recorded before, during and after the fire, at hundreds of predefined spots. In a dense forest, the relative humidity is at least 65%. In transition forest like Tanguro’s, which has about one third of the biomass of its robust neighbor, it comes to 45% at the most, which makes it much more liable to fire.

A dozen sensors coupled to miniaturized computers, to be hung on the trees, store the two kinds of data at every 30 seconds during the burning (at the rest of the time, the interval is 30 minutes). Jennifer Balch, from Yale, responsible for the sensors, chose carefully the trees less inclined to burning for hanging them up, at heights of 5 m, 10 m and 15 m. She was relieved, on the day of the first burning, with the fact that they were all intact (each one costs US$ 180). The mountain of data is going to feed a matrix database on the dynamics of the fire, like its speed and quantity of energy released. Comparing what there is in the database and with the satellite images already on order, the scientists are going to try to calibrate the instruments in orbit, to make them able to read the signature of these fires in the transition forests, which would thus cease to be hidden.

If it works out, this will result in the image of a 100 ha square full of stripes, corresponding to the different lines of fire. Comparing intensity and speed with other variables, such as the time of the fire, the kind of vegetation, presence of clearings and of nests of leaf-cutting ants, the researchers from the Savannization Experiment hope to become capable of foreseeing, from the characteristics of a forest, what the degree of vulnerability to fire is and the probability of it being converted into savanna in a given period of time.

In the light of the size of the threat of savannization, the 300 ha incinerated by the experiment are no more than a match burnt in the midst of a fire at an oil refinery. The igniters take 100 minutes to set fire to 1000 m of their line, with several halts for refueling. It is more time and more fuel that what was forecast, and the second burning, scheduled for 11 o’clock, is postponed to 2 p.m. It is soon 4 p.m. The sun begins to set and a few of the burnings are postponed: the fire is threatening patches that should not be set afire. Half of the team is released and drags itself to the pick-ups, their nostrils and lips covered with soot. Others go on the tractor, used to open up a 5 meter wide firebreak in the neighboring pasture, to be on the safe side. Were it to reach the grass parched by a month without rain, the fire would set off the burning that nobody want to see nor to think about having to put out – a burning for ill.

*Marcelo Leite visited Fazenda Tanguro at the invitation of the Environmental Research Institute of Amazonia (Ipam) and the André Maggi Group.