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HYDROELECTRIC PROJECTS
Large hydroelectric projects, funded by international aid and development organizations like the World Bank, have led to widespread forest loss. Besides inundating large tracts of rainforest (dams in the Amazon are generally ecologically inefficient because large tracts of forest are flooded due to the flatness of the basin) and killing off local wildlife, the dams have the effect of destroying aquatic habitats and affecting fish populations, displacing indigenous peoples, and adding carbon to the atmosphere (as the submerged wood rots). On top of the ecological damage, several projects have silted up from the erosion resulting from deforestation, rendering the dams inefficient. The reduced water flow downstream disturbs riverbeds and affects floodplain farmers who rely on seasonal floods for nutrients to enrich the soil and kill pests. Thus they may turn to pesticides and artificial fertilizers which have their own negative environmental effects. Deltas experience a greater influx of salt water, affecting coastal ecosystems essential to fisheries. Hydroelectric projects are also of concern from a health standpoint because they provide opportunities for the spread of disease-carrying organisms including snails (schistosomiasis/bilharzia) and mosquitoes (dengue fever, yellow fever, malaria).
More on hydroelectric projects
Although "mega-projects" in Latin America are today facing more opposition and being reexamined by the sponsoring parties, hydroelectric projects in Asia are skyrocketing. On the Mekong alone, one of tropical Asia's biologically richest rivers, some 17 dams are planned, while 54 hydroelectric projects are in the works for the Mekong Basin.
POLLUTION
Forests around the world are increasingly affected by air and water pollution, produced from industrial and commercial activities. Besides the pollution caused by oil spills, toxic by-products, and mining accidents, rainforests are seriously degraded by air pollution. Brazil's Atlantic forest was widely damaged in Cubatao (Sao Paulo state) by pollution during the 1970s and 1980s.
Acid rain, expected to increase dramatically in the tropics in the coming years, also takes its toll on tropical forests. 15 percent of the world's remaining tropical forests may soon be affected by acid rain. Similarly, a vast area of forest will be adversely affected by UV-B radiation, should the ozone hole continue to expand.
The dumping of trash and human waste into tributaries from overcrowded cities has resulted in serious pollution in many tropical countries. In some areas, rivers are no longer safe for human use, while plant and animal life suffers.
URBANIZATION
Urban and residential area expansion cause significant forest loss, both in the consumption of building materials and as a source of land. While urbanization can sometimes reduce pressures on forests by the migration of rural residents to population centers, urban and suburban sprawl can be damaging when they occur in frontier settlements and boomtowns. A single gold or gem find can quickly swell a population of a remote forest outpost as a sea of prospectors rush to the area in hopes of finding riches.
Centrally planned urban experiments has resulted in tremendous forest loss in parts of the world. Indonesia's massive Transmigration Program moved some 730,000 families—more than six million people—to the outer islands of Irian Jaya, Borneo, Sumatra, and Sulawesi in an effort to reduce population pressures on the crowded central islands of Java and Bali. The program was generally seen as a failure since many colonists failed to establish successful farms in the hinterlands while large areas of primary forest were cleared. Today some of the worst fires in Indonesia occurs on these once-forested lands.
HUNTING/POACHING
While they are not responsible for deforestation, hunting and poaching cause damage to the rainforest ecosystem by removing species key to the system's functioning. The loss of a certain single species can mean extinction for many others.
The wildlife harvest takes a staggering number of animals: every year in the Brazilian Amazon alone, where 9.6 to 23.5 million mammals, birds, and reptiles are harvested. The annual harvest in the tropical forests of Africa may be 6-12 times that amount, since illegal poaching in Africa is rampant to provide meat for poor rural and urban dwellers.
In Asia, tiger populations have been dramatically reduced due to widespread habitat loss and Chinese demand for traditional medicinal products made from tiger parts. Endangered Sumatran elephants are increasingly poached for their ivory and could go extinct within 50 years at present hunting rates. In Indonesia, where there is a thriving black market for endangered wildlife, orangutans are suffering from both habitat loss and the illegal trapping of baby orangutans for the pet trade. Typically, mother orangutans are killed since they refuse to abandon their young.
In Brazil, Colombia, Nigeria, Madagascar, and other countries, the collection of wild animals for the pet trade takes its toll on local animal populations. Although such collection can be done in a sustainable manner, it rarely is. Reptiles are the fourth biggest commodity after drugs, diamonds, and weapons in the world smuggling trade, but losses are quite high: less than 10 percent of all animals exported illegally make it alive to their final destination—usually a small, dirty aquarium.
INTRODUCTION OF ALIEN SPECIES
While not directly responsible for deforestation, the introduction of foreign plants and animals can cause severe damage to rainforests, especially in delicate ecosystems like islands. These feral species bring new diseases and compete with local species.
The bird life of Guam and Hawaii has suffered from the introduction of alien species. In the case of Guam the culprit was a snake, while in Hawaii the mosquito and domestic chickens were responsible for the decline of native birds. Since the arrival of the Polynesians, at least 62 endemic bird species have disappeared. It is even more startling that Hawaii has more alien plant species than native ones. Alien weeds can choke out endemic plants, especially under disturbed forest conditions like agricultural clearing.
Additionally, alien species can wipe out endemic keystone species that play an important role in the ecosystem, like pollinating certain tree species. The elimination of such an endemic species can spell the end for the tree species and a host of other dependent plant and animal species.
Climate change is expected to increase the number of alien species in some ecosystems.
TOURISM
Tourism can have negative environmental and social effects on the rainforest and its inhabitants. The growing interest in travel to developing countries has spawned a boom in the construction of resorts and hotels on rainforest and mangrove forest lands. Demand by these hotels for tropical hardwood provides another market for woods logged from primary rainforest. Some hotels lack proper waste management and send sewage and trash a few hundred yards offshore where it kills coral reefs and affects sea animals.
Tourists and their money can have profound social effects on local and indigenous communities. In vying for tourist dollars, traditions are forgotten and conflicts arise between members of the community. In some areas, poor villagers turn to prostitution to earn cash from tourists. If tourism is going to provide long term benefits to local people it must be sustainable.
Review questions:
- What environmental problems can dams cause?
- Why are tigers endangered?
- How can alien or invasive species impact the environment?
[full photo version]
Continued: Fuelwood, Roads, Climate
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