Human Life and its effect on the ecology

Today no creature has the ecological impact of man on the aquatic life of the Amazon. Amazonian people almost all live near water. As there are few roads, and even fewer bridges, boats are the only way to move between towns. The waters also supply food to Amazonian people. Within the floodplain about 80% of the protein intake of the population is obtained from fish. Historically, subsistence fishing probably had little impact on fish populations. However, developments over the last 50 years have resulted in an impoverishment of some fish stocks. First, there has been deforestation with white water floodplains. This has resulted in a loss of feeding habitat to fish such as the tambaqui which enter the forest to feed. Second, the demands from rapidly growing cities such as Manaus have increased commercial fishing pressure. In the past commercial fishing boats could not move far from their markets because the catch could not be preserved. Now the boats are fitted with freezers and there are ice making plants in many towns so now even the most remote lakes can be fished.

The other innovation that has had a major impact is the availability of gill nets. These are used by both commercial and subsistence fishermen and can be extremely efficient methods of catching fish. In addition to fishing for food in some regions there has been intensive fishing for the aquarium trade. In the case of the discus of lake Tefe this has had a devastating effect on the local population which is now commercially extinct. It is as yet unclear if the aquarium trade will similarly damage other species. Recent advances in commercial fish breeding are now taking the pressure off some wild stocks.

The impact of man on the aquatic world is not limited to fishing and logging. In the past man hunted manatee, caiman and turtles almost to extinction. Once all of these creatures were to be seen in great numbers. They are now all protected species, but hunting for them still regularly occurs. Once in a small Amazonian town, the town's catholic priest proudly showed me round an orphanage including the freezers that were well stocked with manatee meat. He was so pleased that he had a plentiful supply of meat for the children that I did not have the heart to point out that it is illegal in Brazil to kill manatee. But then on almost any evening in Tefe it is possible to buy barbecued turtle.

The negative impact of man should not lead us to forget that man has lived within the Amazon basin for a long time and is part of the ecosystem. Indeed, it is possible that some types of habitat, including floating meadow and some types of forest, have been modified or made far more extensive because of man. It is even possible that the absence of megafauna within the region, comparable with that seen in Africa, is linked to the distant activities of man. Some believe that man exterminated the giant ground sloths. It is curious that there is a wide spread belief within Amazonia that a large animal, which fits the description of a ground sloth, is still to be found. Could a folk memory of a once existing creature live on long after its death?

Man is now abandoning some areas of the forest to take up urban life. Indeed, in some regions, population density may now be below the level observed by the first Spanish explorers. This population decline may itself produce ecological change that may not all be positive. In many areas, the natives, in order to increase the abundance of fruiting and otherwise productive trees, manipulated the structure of the forest. Such forest may also be able to support more birds, mammals and other frugivores. Could the loss of man result in a decline in biodiversity as the forest reverts to the undisturbed state?
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In the floodplain cattle need to be kept on rafts during the flood season
In the floodplain cattle need to be kept on rafts during the flood season

Preparing the catch for the evening meal. These fish were caught in a few minutes in a floodplain lake and comprise a range of species. The larger fish with eye spots near the tail are the cichlid, Cichla oscillaris, known locally as tucunaré. Other species present include Potamorhina altamazonica and Hemiodopsis sp
Preparing the catch for the evening meal. These fish were caught in a few minutes in a floodplain lake and comprise a range of species. The larger fish with eye spots near the tail are the cichlid, Cichla oscillaris, known locally as tucunaré. Other species present include Potamorhina altamazonica and Hemiodopsis sp

The canoe is the traditional mode of transport throughout the Amazon. When not in use canoes are filled with water to stop the wood drying out and splitting
The canoe is the traditional mode of transport throughout the Amazon. When not in use canoes are filled with water to stop the wood drying out and splitting

A typical fish catch. The photograph was taken in the evening and shows the catch made by one man in about one hour in a varzea lake during the low water season. The large fish on top is an arawana
A typical fish catch. The photograph was taken in the evening and shows the catch made by one man in about one hour in a varzea lake during the low water season. The large fish on top is an arawana

A trapped caiman
A trapped caiman