47.3 Threats to Biodiversity

A study found that introducing multiple enemies of pea aphids increased the yield of alfalfa.

The results of the study show that a diversity of pests is more effective at controlling pests than one single pest.
It will be more difficult to grow food because of the loss of diversity in pest enemies.

In addition to growing crops and raising animals for food, humans get food resources from fish populations.

For 1 billion people, aquatic resources are the main source of animal nutrition.

Since 1990, global fish production has declined.

Most of the world's fisheries are not managed for sustainable development.

A radical restructuring of the marine environment, in which a dominant species is so over-harvested that it becomes a minor player, is what fishery extinctions rarely lead to.

Alterations affect many other species in ways that are difficult or impossible to predict, in addition to humans losing the food source.
Local populations that work in the fishery are affected by the collapse of the fishery.
It will increase the cost of living and limit societies in other ways if populations cannot afford to replace an inexpensive source of protein.
Smaller fish have been taken from the fisheries as larger fish are fished to extinction.
The loss of aquatic systems as food sources could be the ultimate outcome.

There is a video discussing declining fish stocks.

Humans benefit from living in a biodiverse world.

E. O. Wilson is a Harvard entomologist.
He argues that city environments can cause psychological stressors that affect human health and well-being, and that human evolutionary history has adapted us to live in a natural environment.
The hypothesis that the psychological benefits of natural landscapes may hold some truth is based on a lot of research.
There is a moral argument that humans have a responsibility to do little harm to other species.

The combination of human population growth and resource exploitation is a threat to human welfare.

The human population requires resources to survive and grow, and those resources are being removed from the environment unsustainably.
Habitat loss, overharvesting, and the introduction of exotic species are the three greatest threats to biodiversity.
Human population growth and resource use are to blame for the first two.
A fourth major cause of extinction, anthropogenic climate change, is predicted to become significant during this century.
Global climate change is a consequence of human population needs for energy and the use of fossil fuels to meet those needs, but they are not generally seen as threats at the magnitude of the others.

The levels of atmospheric carbon dioxide fluctuate.

The levels of carbon dioxide in the Earth's atmosphere have reached levels never before seen in human history because of the burning of fossil fuels.
The addition of greenhouse gas to the atmosphere is predicted to cause climate change that will have a significant impact on biodiversity in the century to come.

Humans rely on technology to modify their environment and replace functions that used to be performed by the natural environment.

Other species can't do this.
The individuals belonging to the species will be killed if the environment is eliminated.
The species will become extinct if the entire habitat is removed.
Human destruction of habitats increased in the last half of the twentieth century.
Half of Sumatra's forest is gone, but it is home to one species of orangutan, a critically-endangered elephant, and the Sumatran tiger.
The island of Borneo is home to the other species of orangutan.
There is continued forest loss in protected areas of Borneo.
The orangutan is the most visible of thousands of species that will not survive the disappearance of the forests in Sumatra and Borneo.
The forests are removed to make way for plantations of palm oil.
In Europe, palm oil is used in many products.
The five-year estimate of global forest cover loss was 3.1 percent.
In the humid tropics, 272,000 km2 was lost out of a global total of 11,564,000 km2.
There is a species unique to a defined geographic location.

These animals are examples of the diversity of the islands of Sumatra and Borneo.

The (b) Sumatran tiger and the (d) Sumatran elephant are critically threatened species.
This oil palm plantation in Borneo's Sabah Province is being made way for rainforest habitat.

Home improvement products may be contributing to habitat loss and species extinctions.

The market for illegally harvested tropical timber is huge, and the wood products often find themselves in building supply stores in the United States.
The United States is the world's largest consumer of wood products and 10 percent of the imported timber stream is potentially illegal.
In 2006 it was $3.6 billion.

Some producers' products may not have certification while other products are.

There are other certifications that are unreliable due to lack of independence from the industry.
Domestic wood species can be bought.
It would be great if there was a list of legal and illegal wood products.
What is illegal in one country may be legal in another.
Whether a wood product will be certified by the FSC depends on a number of factors.
It is always a good idea to ask questions about where the wood came from and how the supplier knows it was legal.

Habitat destruction can affect other things.

Land development, damming, channelizing, and water removal are some of the ways in which rivers and streams are altered.
Damming affects the water flow to all parts of a river, which can affect populations that had adapted to the natural flow of the river.
An estimated 91 percent of the United States rivers have been altered.
Modifications include dams, levees, and dredges to create land that is more suitable for human development.
The United States has seen declines in many fish and amphibian species due to river damming.

Many species are at risk of being overharvested, particularly aquatic species.

There are recent examples of fishery collapse despite regulation and monitoring.
The western Atlantic cod fishery is significant.
The introduction of factory trawlers in the 1980s caused it to become unsustainable, as it was a hugely productive fishery for 400 years.
The collapse of the fish industry is a result of both economic and political factors.
Even when the fishing territory is within a country's territorial waters, the resources are managed as a shared international resource.
It's a common outcome of overexploitation.
When access to the fishery is open and unregulated, fishers have the ability to overfish.
If time and money were invested elsewhere, the biological growth of the resource would be more than the potential growth of the profits made from fishing.
Economic forces will always drive toward fishing the population to extinction.

The Fish & Wildlife Service has an interactive map of critical habitat.

The last fish of a species is rarely fished out of the ocean.

The extinction of fish species is still harmful.
True extinction is a possibility in some instances.
Due to low reproductive rates, whales are at risk of extinction through hunting.
Some sharks are at risk of extinction.
The groupers are a population of slow-growing fishes in the Caribbean that are at risk of extinction from being overfished.

Coral reefs face immediate peril from several processes.

1/3 of the world's marine fish species are found on the Reefs.
Most home marine aquaria have wild-caught organisms.
There are studies showing that populations of some species have declined in response to harvesting, indicating that the harvest is not sustainable at those levels.
There are concerns about the effect of the pet trade on some species.

There is a brief video discussing the role of marine ecosystems in supporting human welfare and the decline of ocean ecosystems.

In parts of Asia and Africa, hunting practices are thought to be threatening a number of species with extinction.

Bush meat in Africa used to be hunted to feed families directly, but recent commercialization of the practice has increased harvest rates to the level of unsustainability.

Human population growth has increased the need for food that isn't being produced in agriculture.
The bush meat trade is threatening mammals and other primate species.

Kudzu was introduced in the United States in 1876.

It was planted to conserve soil.
It can grow up to a foot a day in the southeastern United States.
It covers over 7 million acres in the southeastern United States.
If an introduced species is able to survive in its new habitat, that is reflected in the observed range of the species.
Human transportation of people and goods, including the intentional transport of organisms for trade, has dramatically increased the introduction of species into new ecosystems, sometimes at distances that are well beyond the capacity of the species to ever travel itself and outside the range of the species' natural predators.

Most exotic species introductions fail because they don't have enough individuals to adapt to the environment they enter.

Pre-adaptations can make some species more successful in a new environment.
Dramatic population increases in their new habitat can threaten the species that exist there.
Exotic species are also called invaders.
Exotic species can threaten other species.
The spotted knapweed, also known as the Eurasian star thistle, has invaded and rendered useless some of the open prairies of the western states.
It is a great flower for the production of honey and supports many pollinating insects, including monarch butterflies in the north-central states.

Lakes and islands are vulnerable to extinction threats.

The introduction of the Nile perch in Lake Victoria caused the extinction of about 200 species of endemic cichlids.
The introduction of the brown tree snake via aircraft from the Solomon Islands to Guam in 1950 has led to the extinction of three species of birds.
Several other species are in danger.
One of the brown tree snakes was found on an aircraft arriving in Texas.
The airport, military, and commercial aircraft personnel need to be on their toes to prevent the snake from moving from Guam to other islands in the Pacific.

Because of their isolation from mainland ancestors, islands have a disproportionate number of endemic species.

The brown tree snake, Boiga irregularis, has caused numerous extinctions on the island of Guam since it was accidentally introduced in 1950.

The African clawed toad (Xenopus laevis) is a commonly used laboratory and pet species and may have been the cause of the spread of the fungus.

It is possible that biologists are responsible for spreading the disease.
The North American bullFrog, Rana catesbeiana, which has also been widely introduced as a food animal but which easily escapes captivity, can act as a reservoir for the disease.

It is a predator in freshwater lakes.

The Limosa Harlequin Frog, an extinct species from Panama, died from a disease.

The red tumors are indicative of the disease.

The Indiana bat, Myotis sodalis, and the Virginia big-eared bat are threatened with extinction because of the disease.

It's not clear how the fungus was introduced, but it's likely that recreational cavers brought it to Europe.

The little brown bat was found in Vermont.

extinction rate estimates range from 15 percent to 40 percent of species destined for extinction by 2050, with scientists disagreeing about the likely magnitude of the effects.
Climate change will alter regional climates, including rainfall and snowfall patterns, making habitats less hospitable to the endemic species.
The warming trend will force species to move with their adapted climate norms while facing habitat gaps along the way.
New competitive regimes will be imposed on species as they find themselves in contact with other species that are not in their historic range.
polar bears and grizzled bears have an unexpected contact.
The two species had different ranges.
There are documented cases of these two species mating and producing viable offspring, which may or may not be viable crossing back to either parent species.
Changing climates make it harder for species to adapt to seasonal food resources and breeding times.
There are many mismatches to shifts in resource availability.

Climate change is thought to be the reason why grizzly bears have been spotted farther north than in the past.

The polar bear habitat overlaps the grizzly bear habitat.
Historically, the two species of bears, which are capable of producing viable offspring, lived in different habitats and never met.
In 2006 a hunter shot a grolar bear, the first wild hybrid ever found.

Some European bird species ranges have moved northward.

The optimal shift based on warming trends was double the distance, suggesting that the populations are not moving quickly enough.
In plants, butterflies, other insects, freshwater fishes, reptiles, and mammals, range shifts have been observed.

Climate change will move up mountains, eventually crowding species higher in altitude and eliminating the habitat for those that are adapted to the highest altitudes.

Some climates will disappear.
The formation of sea ice is greatly reduced by the rate of warming in the arctic.
The only reliable source of food for polar bears and other species is the ice.
Sea ice coverage has been decreasing since the mid-twentieth century, and the rate of decline observed in recent years is far greater than previously predicted.

Global warming will raise ocean levels due to meltwater from glaciers.

A number of islands will disappear and some species will be affected by the reduction of island size.

A cycle that has provided freshwater to environments for centuries will also be jeopardized by the gradual melting of the poles, glaciers, and higher elevation mountains.
There could be a shortage of fresh water.