The pothole region has experienced temporary droughts in the past. However, a permanently warmer, drier future may lead to a threshold change—a dramatic drop in the prairie potholes that host waterfowl populations, which subsequently provide highly valued hunting and wildlife viewing opportunities.
Similarly, when coral reefs become stressed from increased ocean temperatures, they expel microorganisms that live within their tissues and are essential to their health.
This is known as coral bleaching. As ocean temperatures warm and the acidity of the ocean increases , bleaching and coral die-offs are likely to become more frequent.
Chronically stressed coral reefs are less likely to recover. Climate change and shifts in ecological conditions could support the spread of pathogens, parasites, and diseases, with potentially serious effects on human health, agriculture, and fisheries. For example, the oyster parasite, Perkinsus marinus , is capable of causing large oyster die-offs.
This parasite has extended its range northward from Chesapeake Bay to Maine, a mile expansion tied to above-average winter temperatures.
To learn more about climate change impacts on human health, visit the Health Impacts page. Climate change, along with habitat destruction and pollution, is one of the important stressors that can contribute to species extinction.
Settele, J. Scholes, R. Betts, S. Bunn, P. Leadley, D. Nepstad, J. Overpeck, and M. Terrestrial and Inland Water Systems. Part A: Global and Sectoral Aspects. Field, C. Barros, D. Dokken, K. Mach, M. Mastrandrea, T. Bilir, M. Chatterjee, K. Ebi, Y. Estrada, R. Genova, B. Girma, E. Kissel, A. Levy, S. MacCracken, P. Mastrandrea, and L. White eds. A Report by the U. Backlund, P. Janetos, D. Schimel, J. Hatfield, K.
Boote, P. Fay, L. Hahn, C. Izaurralde, B. This will deteriorate ecosystems, particularly if they are used unsustainably. Overall, human health is expected to improve in the future in most scenarios.
Only the scenario which combines regionalization with reactive ecosystem management might lead to a negative spiral of poverty , declining health, and degraded ecosystems in developing countries. However, both proactive and reactive approaches have costs and benefits.
The importance of ecosystem services for human well-being around the world was investigated at local, national, and regional levels. Overall, the global and sub-global assessments gave similar results on the present state of ecosystems. However, local conditions were sometimes better or worse than expected from the global assessment, for instance for water resources or biodiversity.
The assessments identified an imbalance in the distribution of the benefits and costs of ecosystem change , since these are often displaced or postponed. Some ecosystem problems have been reduced by innovative local responses. Therefore, institutions are needed at multiple levels to strengthen the adaptive capacity and effectiveness of sub-national and local responses.
In general, people manage ecosystems in such ways that short-term benefits are increased, while long-term costs go unnoticed or are ignored. This can transfer the costs of current changes to future generations. Different drivers of ecosystem change take more or less time to react to changes.
For example, some species might become extinct quickly when they lose their habitat , but for others, like trees, it can take centuries. This delay provides opportunities for restoring habitats and rescuing species.
Other changes are more difficult to predict, because they are gradual only until they reach a certain threshold , at which large changes occur suddenly. Examples of abrupt changes include the start of epidemics, the collapse of a fish population , and bursts of algae growth. Loss of biodiversity , for instance, makes it more difficult for ecosystems to recover from damage. Once an ecosystem has undergone an abrupt change, recovery to the original state is slow, costly, and sometimes even impossible.
Changes in policy can decrease many of the negative consequences of growing pressures on ecosystems. However, the actions needed for this are much larger than those currently taken. Most ecosystem services have already suffered, but the damage would have been even greater without the conservation actions taken so far.
Examples of actions include: increasing international coordination, developing and diffusing technology, and improving the use of information. Reducing some important uncertainties about ecosystems and their services could significantly improve the ability of assessments to provide the information needed by policy-makers. Better theories and models are needed to understand the links between ecosystem change and impacts on human well-being and to assess the economic consequences of ecosystem change.
Moreover, not enough is known about the importance placed by different cultures on cultural services , how this changes over time, and how it influences trade-offs and decisions. Direct drivers may also be human influenced. The introduction of a species not normally associated with a particular ecosystem — such as kudzu, silver carp or zebra mussels — has a devastating impact on that ecosystem. Most ecosystem changes occur over time rather than as a result of a single, sudden event.
Scientists call one such slow process ecological succession. As this process plays out, species populations fluctuate and sometimes disappear entirely. A new species entering the ecosystem — such as the bear or mountain lion example — is one possible trigger to launch ecological succession.
Evolutionary changes that improve a particular species' adaptation is another driver. For instance, depleted food sources might change migration patterns, or one species might adapt behaviors that allow it to best its competitor species.
Ecological changes to one species often influence the adaptation of others. When plants first developed flowers millions of years ago, insects adapted an attraction to nectar which had the benefit of spreading plant pollen. The sheer destructive force of storms, floods, tropical storms and tornadoes often impact ecosystems. Algal blooms and fish kills: Excessive nutrient loading causes eutrophication of freshwater and coastal ecosystems.
While small increases in nutrient loading often cause little change in ecosystems, once a threshold is reached the changes can be abrupt and extensive, causing bursts of algae growth. Severe eutrophication can kill animal life in the water by causing oxygen-depleted zones. Collapse of fisheries : Collapses of fish populations have been common in both freshwater and marine fisheries. A moderate level of catch often has a relatively small impact, but with increasing catches a threshold is reached where too few adult fish remain to produce enough offspring to support this level of harvest.
For example, the Atlantic cod stocks of the east coast of Newfoundland collapsed in , forcing the closure of the fishery see Figure 3. Species introductions and losses can also cause non-linear changes in ecosystems and their services. For example, the loss of the sea otters from many coastal ecosystems on the Pacific Coast of North America due to hunting led to a boom of sea urchin populations a prey species for otters which in turn led to the loss of kelp forests which are eaten by urchins.
Changes in dominant species in coral ecosystems: Some coral reef ecosystems have undergone sudden shifts from coral-dominated to algae-dominated reefs. Such abrupt shifts are essentially irreversible, and once a threshold is reached the change takes place within months. In Jamaican reef systems, centuries of overfishing of algae-grazing species contributed to a sudden switch leading to low diversity, algae-dominated reefs with very limited capacity to support fisheries.
Regional climate change : The vegetation in a region influences climate through affecting the amount of sunlight which is reflected, the amount of water released by plants to the atmosphere, and the amount of wind and erosion.
In the Sahel region, vegetation cover is closely linked to rainfall. When vegetation is present, rainfall is quickly recycled, generally increasing precipitation and, in turn, leading to denser vegetation. Land degradation reduces water recycling and may have contributed to the rainfall reduction in the Sahel region during the last 30 years.
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