Drivers of biodiversity loss - IV - Over-exploitation or Over- harvesting of Animals and Plants
The five important drivers of biodiversity loss are
1. Habitat loss and degradation
2. Pollution
3. Invasive species
4. Over-exploitation
5. Climate change associated with global warming
4. Over-exploitation or Over- harvesting of Animals and Plants
More than one- third of the world’s endangered birds, fish and mammals are threatened directly by human activities such as fishing, hunting, and trading for meat and other commodities.
Wild animals are captured as pets or for skins or other luxury items while plants are taken for gardens or as ingredients in herbal medicines.
Overfishing
For millennia, the oceans supplied fish and seafood to us without any noticeable decrease in the fish populations due to their high reproductive potential. But the industrialized fishing and exploding human populations increased the demand on fisheries that resulted in overfishing.
Fishery collapse also affect rest of the ecosystem, such as decrease in seabirds population, increase in sea urchins population, etc.
Consumers can play a role in reducing overfishing by buying fish and seafood wisely. Information on whether fish and seafood is being harvested sustainably can be found online in lists kept by the Blue Ocean Institute (Guide to Ocean Friendly Seafood), Environmental Defense (Oceans Alive), and the Monterey Bay Aquarium (Seafood Watch Program).
Hunting
Early humans hunted animals for food, warm clothing, and other commodities. As agriculture developed, farmed foods provided people’s diet and Hunting became a sport such as big-game hunting or trophy hunting. Favorite targets are moose, caribou, bear, and elk in North America; reindeer, elk, and wolf in Europe; tiger, leopard, elephant, and wild goat in Asia; and antelope, gazelle, zebra, leopard, lion, giraffe, rhinoceros, and elephant in Africa
Innumerable species have been hunted nearly to extinction, examples are buffalo, passenger pigeon and cheetah.
When Europeans arrived in Colonial America many animals were hunted into extinction or near extinction. The American bison or the buffalo, covered the Great Plains of the United States and Canada, with a population of about 30 million. The railroad companies paid hunters to destroy the herds so that the animals did not interfere with trains by standing on the tracks. Hunting bison was also done to prevent the sustenance of the Native American tribes who were at war with the United States. By 1890, there were fewer than 750 bison left, all in zoos or protected areas.
Passenger pigeons were hunted to the last bird. They were the most abundant bird species on Earth, they lived in enormous flocks; the largest flock, of 2 billion birds even darkened the sky for several days as it flew overhead. Because passenger pigeons lived close together and were slow flyers, they were extremely easy to hunt and their meat was so cheap and was fed to hogs and slaves. The last remaining flock, approximately 250,000 birds, was killed by sport hunters in a single day in 1896. The very last passenger pigeon died in captivity in 1914.
Species of marine mammals primarily whales, dolphins, seals, sea lions, sea otters are also being hunted to extinction or near extinction for their fur, oil, and meat.
The Marine Mammals Protection Act of 1972 bans taking (harvesting, hunting, capturing, or killing, or attempting to do so) or importing any marine mammals or mammal products in United States territorial waters and fisheries. Hunting land animals in developed nations is now highly regulated. These laws save significant populations of game animals and birds.
Professional hunters are sometimes hired to control animals in populated areas, such as bears in parks.
Wildlife Trade
The sale and exchange of wild animals and plants and the products made from them is known as the wildlife trade. Plants are gathered from the wild and sold for gardens or herbal medicines; animals are sold as pets, or for food, exotic leather products, furs, musical instruments, and medicines. Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) by the United Nations prohibits international trade in threatened or endangered organisms, which now include more than 28,000 species of plants and 5,000 species of animals.
Bushmeat
Bushmeat is commercially hunted wild animal meat, often from Africa. Recent studies show that between one and five million tons of wild animal meat are taken annually from the Congo Basin in West Africa. This is making the wild life there unsustainable.
Of the seven great ape species, only humans are not facing extinction. The reasons for the decline are habitat loss, pathogens, and the rise in the bushmeat trade. Besides humans infecting apes with deadly diseases, African apes and monkeys harbor pathogens that can get transmitted into human populations. The introduction of HIV into humans has been traced to the consumption of chimpanzee meat.
China is also involved in wild animal meat. There is high demand for exotic foods such as pangolin, a slow-moving anteater.
Exotic Pet Trade
Exotic pets are animals that have not been domesticated and often do not live well with humans, and yet the trade thrives, especially in the United States, the European Union, and Japan. Examples are baboons, chimpanzees, rhesus monkeys, tigers, lions, wolves, black bears, three-toed sloths, foxes, raccoons, snakes, tarantulas, scorpions, turtles, lizards, birds and coral reef fish.
Wild animals spread disease to domestic animals and humans. Salmonella infection from reptiles, Herpes B virus from macaque monkeys, etc are examples
Medicinal Plants
80% of the world’s people use traditional medicine to treat illnesses which require medicinal plants. China and India are the largest markets for medicinal plants.
For more than 3,000 years, the Chinese are using natural ingredients from plants, animals, and minerals to cure everything from the common cold to fevers, arthritis, and sexual dysfunction. These medications are sold throughout China and other Asian countries and to Asians around the world. Traditional Chinese medicines use ingredients from hundreds of species of plants and animals including endangered, threatened, or protected species.
Most medicinal plants are gathered from the wild and are an important income source. Wild Asian ginseng cost tens of thousands of dollars per kilogram. To protect wild medicinal plants, regulations must be enforced and cultivation of medicinal herbs should become more widespread.
5. Climate change associated with global warming
Climate change has been an important factor for evolutionary processes and caused extinctions throughout Earth history. Human activities, such as fossil-fuel and forest burning results in a rapid change in Earth’s climate resulting in global warming. Amphibian species are undergoing extinction since global warming has allowed pathogens increase.
Global Warming
Since the end of the Pleistocene ice ages about 10,000 years ago, 4°C rise in global temperatures have occurred.
Each plant and animal species have an optimal climate condition to which they are adapted. Global warming alters the climatic conditions at regions which becomes intolerable for some species which may either move toward the poles or to higher elevations until it finds conditions where it can grow. Those species that cannot move or adapt to the new conditions will be extinct.
Increasing temperatures are melting glaciers and ice caps which destroys the habitat required for polar bears and northern seals. Melting ice results in rise of sea level which alter the coastal areas that habitat numerous species.
Temperature changes affect the breeding of some animal species, some populations decrease and some populations increase.
The sex of some aquatic animals, such as some turtles and fish, which are determined by water temperature and warmer water leads to all-female turtle hatchlings
Since most pathogens thrive in a warm environment, global warming increase both their survival and transmission rates. Most disease vectors are now capable of completing their life cycle in a faster rate. About one-third of forests are affected by climate change due to increased risk of pathogen attack and problems associated with drought.
Global warming is occurring at a faster rate so that many plants and animals are not able to adapt before they suffer population decline or even extinction. The most detrimentally affected are the amphibian populations.
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References
- Emerging Consequences of Biotechnology - Biodiversity Loss and IPR Issues, Krishna Dronamraju, World Scientific Publishing Co. Pte. Ltd.
- Biosphere - Ecosystems and Biodiversity Loss, Dana Desonie, Chelsea House
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