21.2 Threats to Biodiversity

Chapter 21 will make it more difficult to grow food.

The world's growing human population faces significant challenges in the increasing costs and difficulties associated with producing food.

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

For a billion people, aquatic resources are the main source of food.
Since 1990, production from global fisheries has declined.
Few fisheries on Earth are managed.

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 human 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 larger fish in the past.
The loss of aquatic systems as food sources could be the ultimate outcome.

There is a video about a study of declining fisheries.

The combination of human population growth and resources used by that population is the core threat to biodiversity and therefore 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 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, human-caused 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 are not generally seen as threats at the magnitude of the others.

The levels of atmospheric carbon dioxide fluctuate.

The burning of fossil fuels in recent history has caused a dramatic increase in the levels of carbon dioxide in the Earth's atmosphere, which have never before been seen on Earth.
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 in the species will be killed if their habitat is eliminated.
Unless they are one of the few species that do well in human-built environments, the species will become extinct if the entire habitat is removed.
Human destruction of habitats accelerated in the last half of the 20th 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 in Borneo is the most visible of thousands of species that will not survive the disappearance of the forests of Borneo.
The forests are removed to make way for plantations of palm oil.
In Europe, palm oil is used in many products.
The 5-year estimate of global forest cover loss was 3.1 percent.
In the humid tropics, forest loss is mostly from timber extraction.
The extinction of species unique to those areas is represented by these losses.

An oil palm plantation in Sabah province Borneo, Malaysia, replaces native forest habitat that a variety of species depended on to live.

Home improvement products may be contributing to habitat loss and species extinctions, but most consumers don't think about it.
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.
Most of the illegal products are imported from countries that act as middleman.

One way to ensure that the wood has not been taken illegally from a tropical forest is to look for their certification on flooring and other hardwood products.

Some producers' products may not have certification while other products are.
There are certifications other than the FSC that are run by timber companies.

Domestic wood species can be bought.

It would be great if there was a list of legal and illegal woods.
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.
Asking questions about where the wood came from and how the supplier knows it was legal is always a good idea.

Habitat destruction can affect other things.

Habitat modification through damming or water removal is often the target of rivers and streams.
Access to parts of a river is affected by damming.
Populations that are adapted to seasonal changes in flow can be reduced or eliminated by changing a flow regime.
The United States has an estimated 91 percent of river lengths modified with damming or bank modifications.
Many fish species in the United States have seen declines due to river damming and habitat loss.
According to research, species of salamanders that must carry out parts of their life cycles in both aquatic andterrestrial habitats are at greater risk of population declines and extinction because of the increased likelihood that one of their habitats will be lost.
This is of particular concern because the amphibians have been declining in numbers and going extinct more rapidly than other groups.

A serious threat to aquatic species is overharvesting.

There are scientists that have collapsed.

The recent collapse of the western Atlantic cod fishery is spectacular.
The introduction of factory trawlers in the 1980s led to it becoming unsustainable, as it was a hugely productive fishery for 400 years.
The causes of fishery collapse are both political and economic.

Even when the fishing territory is within a country's territorial waters, most fisheries are available to anyone willing to fish.

Overexploitation is the general outcome of harvests of resources.
Large fisheries are regulated to try to avoid this pressure, but it still exists in the background.
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 drive toward fishing the population to extinction.

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

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

There are instances in which extinction is a possibility.
The 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 peril from a number of processes.

1/3 of the world's marine fish species are found on the Reefs.
Most home marine aquaria have coral reef species that are wild-caught.
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.

The decline of ocean ecosystems can be seen as a role of marine ecosystems in supporting human welfare.

In parts of Asia and Africa, hunting practices are thought to be threatening several 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.

Many monkeys and the great apes are threatened by the bush meat trade.

The intentional transport of organisms for trade has dramatically increased the introduction of species into new environments.

These new introductions can be very far away from the natural 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.

Some species have characteristics that make them successful in a new environment.
Dramatic population increases in their new habitat can threaten the species that exist there.
The exotic species becomes an invader when this happens.
Invasive species can threaten other species.

Lakes and islands are vulnerable to extinction threats.

The introduction of the Nile perch in Lake Victoria caused the extinction of 200 species of 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 water from the port of origin is pumped into the tanks of the empty ship.

Living organisms are found in the water from the ocean or estuary of the port.

The ship takes cargo at the destination port, which may be on a different continent.

The zebra mussel was introduced to the Great Lakes prior to 1988.
The Great Lakes have caused the industry millions of dollars in clean up costs.
The ecology of the lakes has been altered by the mussels.
They benefit some species, such as smallmouth bass.
The improved water clarity has allowed aquatic plants to grow along shorelines, which in turn has provided shelter for young fish.
The abundance of native clams and crabs has been dramatically reduced by the crabs.

Disease organisms can also be invading exotic species.

It is possible that biologists are responsible for spreading the disease.

The red tumors are indicative of the disease.

It is not known how the fungus was introduced, but it is likely that recreational cavers brought it to Europe.

The little brown bat was found in Vermont.

When combined with other threats such as habitat loss, climate change is seen as a major extinction threat.

Anthropogenic warming of the planet has been observed and is believed to continue due to past and continuing emission of greenhouse gases, primarily carbon dioxide and methane, into the atmosphere caused by the burning of fossil fuels.
Earth is able to emit heat energy from the sunlight when it enters the atmosphere.
Our understanding of the changes in climate and energy balance is dependent on predictions from computer models.
Dramatic and dangerous climate changes are likely in the coming decades because scientists agree the present warming trend is caused by humans.
There is still debate and a lack of understanding.
Estimates of the magnitude of the effects on extinction rates range from 15 to 40 percent.
Climate change will alter regional climates, including rainfall and snowfall patterns, making habitats less hospitable to the species living in them.
The warming trend will cause species to move towards the north and south poles, but also to face 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 mate and produce viable offspring.
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 and timing documented by scientists.

The ranges of European bird species have moved northward on average.

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, amphibians, 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 rate of warming appears to be accelerated in the northern part of the world, which is considered a serious threat to polar bear populations that need sea ice to hunt seals during the winter months.
Since the mid-twentieth century, there has been a decrease in sea ice coverage.
Climate models had predicted a decline in the rate of decline.