Climate change is starting to have major impacts on ecosystems. With global temperature rising, there is a decrease in snow-fall, and sea levels are rising. Ecosystems will change or evolve to cope with the increase in temperature. Consequently, many species are being driven out of their habitats.
Polar bears are being threatened. They need ice for hunting seals, their primary prey. However, the ice caps are melting, making their hunting periods shorter each year. As a result, the polar bears are not developing enough fat for the winter; therefore, they are not able to reproduce at a healthy rate.
Fresh water and wetland ecosystems are dealing with extreme effects of the increase of temperature. The climate change could be devastating to salmon and trout and to other aquatic life. The increase in temperature will disrupt the current life patterns of the salmon and trout. The cold-water fish will eventually leave their natural geographical range to live in cooler waters by migrating to higher elevations.
While many species have been able to adapt to the new conditions by moving their range further towards the poles, other species are not as fortunate. The option to move is not available for polar bears and for some aquatic life.
Vast numbers of species are being annihilated. Every year between 17,000 and 100,000 species vanish from the planet. The speed in which species are becoming extinct is much faster than in the past. The last mass extinction was caused by a meteor collision 65 million years ago.
The loss of new species in an ecosystem will eventually affect all living creatures. In the U.S. and Canada, there was a dramatic reduction of shark population along the U.S. east coast. Since then, there has been an increase in population of rays and skates, which in turn has decimated the population of shellfish. The loss of shellfish has reduced the water quality and the size of sea grass beds. Biodiversity is being lost at a fast rate. The more species there are in an ecosystem, the more resilient it is to evolution.
Seven million square kilometers of tropical forest have vanished in the last 50 years. About two million square kilometers were used for crops, while the remaining five million square kilometers is poor quality land. Turning these unproductive lands back into native forest could capture an estimated five billion metric tons of carbon from the atmosphere every year for 10 to 20 or more years. Reforestation will have enormous benefits on biodiversity.
In the wilderness, the problem of animal overpopulation is solved by predators. Predators tend to look for signs of weakness in their prey, and therefore usually first eat the old or sick animals. This has the side effects of insuring a strong stock among the survivors and controlling the population.
In the absence of predators, animal species are bound by the resources they can find in their environment, but this does not necessarily control overpopulation. In fact, an abundant supply of resources can produce a population boom that ends up with more individuals than the environment can support. In this case, starvation, thirst, and sometimes violent competition for scarce resources may effect a sharp reduction in population, and in a very short lapse, a population crash. Lemmings, as well as other less popular species of rodents, are known to have such cycles of rapid population growth and subsequent decrease.
In an ideal setting, when animal populations grow, so do the number of predators that feed on that particular animal. Animals that have birth defects or weak genes (such as the runt of the litter) also die off, unable to compete over food with stronger, healthier animals.
In reality, an animal that is not native to an environment may have advantages over the native ones, such being unsuitable for the local predators. If left uncontrolled, such an animal can quickly overpopulate and ultimately destroy its environment.
Examples of animal overpopulation caused by introduction of a foreign species abound.
Some common examples of ecological crises are: