Imprimir Republish


Accurate Vision

Method lowers the cost of mapping and classifying vegetation in the Pantanal

Could a single-engined Cessna 206 be more useful to the Pantanal than the Landsat, Nasa’s remote sensoring satellite? For a group of researchers at the Brazilian Farming Research Company (Embrapa) at Corumbá, in Mato Grosso do Sul, the reply could be yes. Inspired by Australian colleagues, who have been making flyovers periodically since the 60’s to monitor dolphins and the great land vertebrates in Oceania, they go up – every other year – in one of these little planes and fly over the immense Center-West plain with just one mission: to record examples of the plant and animal species they see.

Back on the ground, they organize the data collected, make calculations, and produce a detailed map of the types of vegetation found and an x-ray of the progress of the selected animal populations in their main habitats. All this is cheap and efficient according to the researchers at the Pantanal Embrapa. “The Landsat images are good tools for general observation: they can show broad trends, say whether there is more or less green area in a given place. But they cannot distinguish between the different types of vegetation. They merely show whether there are trees, grass or water in a region”, says the zoology technician Marta Pereira da Silva, who is involved in the work.

“For the satellite sensor, an area of cerrado (type of wooded savanna) and another of semi-deciduous woodland, which are different especially because they have distinct species of tree, could be the same thing”. The remote sensoring has another disadvantage: it does not enable observation and classification of the fauna in a given habitat, one of the trump cards of aerial surveying. With the aerial observations, Marta and her colleagues have identified 16 types of green cover, detailed in an article published in the Brazilian Botanical Magazine.

Similar and covering neighboring land, the cerradão or forested savanna areas (dense formation with 8 to 20 meter-tall trees that partially lose their leaves in the dry season) and the cerrado or treed savanna (sparse, smaller bushes and trees no more than 10 meters tall, growing on grassy ground) are the main types. Found in the eastern and central part of the central plain, in areas of sandy soil, the forested and treed savanna form 22.1% and 14.3% respectively of the vegetation in the Pantanal.

Another two types of woodland are less common. Located principally in the north of the region, semi-deciduous forests (tall, 8- to 20-meter trees that lose their leaves in the dry season) account for 3.9% of the vegetation coverage. Riverside forest, along the banks of the rivers is less common (2.4%). Almost as abundant as the forest and woodland, the areas of treeless plain, with grassy and herbaceous vegetation, were amply found. The dry plain accounted for a little more than 20% of the area’s green covering. The floodplains so-called because they do in fact flood when the rivers are in their high water period accounted for almost 11% and are concentrated in the west of the Pantanal, near the river Paraguay. The numerous areas of marshland also called attention (7.4%).

Deer threatened
Besides these particularly prominent areas, there were other more unobtrusive presences such as the chaco (spiny bushes with small leaves that fall in the dry season and in winter) and the baceiros or batumes (floating islands of densely rooted aquatic plants). Finally, Marta’s team detected areas with a great concentration of a particular species of tree: trithrinax palm, buriti palms, babaçu palms, beak sedge woodland, lantana shrubs, senna and the Brazilian roupala. The survey also disclosed that almost 6% of the Pantanal is under water.

In terms of fauna, the researcher focused on three species in the 16 habitats of the plain in clustered and Mato Grosso do Sul: jacaré-do-pantanal (Caiman c. yacare), cervo-do-pantanal (Blastocerus dichotomus) and veado-campeiro (Ozotocerus bezoarticus). The estimated cayman population is 3.9 million, but the technicians believe there could be as many as 10 million. The number of deer is around 44,000 and, it has been unchanged in the last decade. “The only one of these creatures really threatened with extinction is the red deer”, says the biologist Rodiney Mauro, who is part of the aerial survey group.

Since the beginning of the last decade, the number of red deer has shrunk by 30% a year. “With the growth of the areas under pasture and farming projects the environment par excellence for this species – dry plains or savanna with few trees – has shrunk”, says Mauro. In addition to human activity, the skies have also reduced the red deer’s vital space. The abundant rainfall in the 90s, flooded areas normally free from inundation, corralling the animal in ever smaller areas. Nowadays, the red deer exist essentially in the center of the Pantanal; there are none in the south, and very few in the north.

The crew
For the aerial survey of the Pantanal, an area covering 140,000 square kilometers – at least 1.5% of Brazil – the researcher rented a single-engine four- or six-seater. Besides the pilot and, perhaps, a navigator – the pilot can do both jobs -, there is a technician who notes down the vegetation and two or even three who collect the data on the fauna. To facilitate the observation of animals, each notes down only one or two species.

Embrapa’s methodology divides the plain of the Pantanal into 50 east-west sections, with space of around 10 kilometers between each. A section is a straight-lined band to be covered by the aircraft. The over-flight is done when there is less rain, between September and October, when the task of identifying the species is easier and more productive.

Fast game
As soon as the aircraft takes off and reaches its cruising altitude – 60 meters -, the researchers barely have time to breathe. The speed of the annotation takes ones breath away. Every 36 geographical seconds covered, approximately 1 kilometer, the navigator calls out. It is the signal to the other crew members to note down on a form what they are seeing in the area below: the type of vegetation and its quantity – low, medium or high density – theanimal species and how many of them. As the aircraft travels at 200 kilometers an hour, in practice there is a fresh annotation to be made every 18 seconds. At the conclusion of the mapping, 11,570 annotations have been made.

After plotting the Pantanal five times, the last time in 2000, the researchers, know that around 100 hours of flying time are needed to cover the area properly. Given that an hour’s flight costs around R$ 200, mapping the Pantanal means spending R$ 20,000 on renting the aircraft. It is not expensive if we allow for the price of images obtained by remote sensoring. Just one satellite photo costs between R$ 800 and R$ 1,200 – and at least 15 are needed to cover the whole of the Pantanal. “The method is relatively cheap. Its results prove compatible with the data from remote sensoring, with the advantage of giving additional information and it can be used for various purposes”, comments Marta.

Green profile of the Pantanal
The proportion of each type of vegetable cover in the region (as a percentage of the total area)

Cerrado 22.1
Dry plain 20.3
Forested savanna (Cerradão) 14.3
Floodplains 10.8
Marshland 7.4
Semi-deciduous forest 3.9
Cambarazal 3.1
Riverside forest 2.4
Baceiro or batume 2.4
Lantanas 2.3
Sennas 1.7
Canjiquas 1.2
Piri/virgin forest 1.2
Chaco 0.5
Babaçu palms 0.3
Murity palms 0.2
Areas under water 5.9Source: Embrapa