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Freshwater ecosystems are among the earth aquatic ecosystems. They include lakes and ponds, rivers, streams and springs, and wetlands. They can be contrasted with marine ecosystems, which have a larger salt content. Freshwater habitats can be classified by different factors, including temperature, light penetration, and vegetation.
Humankind benefits from a multitude of resources and processes that are supplied by natural ecosystems. Collectively, these benefits are known as ecosystem services and include products like clean drinking water and processes such as the decomposition of wastes. While scientists and environmentalists have discussed ecosystem services for decades, these services were popularized and their definitions formalized by the United Nations 2004 Millennium Ecosystem Assessment (MA), a four-year study involving more than 1,300 scientists worldwide. This grouped ecosystem services into four broad categories: provisioning, such as the production of food and water; regulating, such as the control of climate and disease; supporting, such as nutrient cycles and crop pollination; and cultural, such as spiritual and recreational benefits.
As human populations grow, so do the resource demands imposed on ecosystems and the impacts of our global footprint. Natural resources are not invulnerable and infinitely available. The environmental impacts of anthropogenic actions, which are processes or materials derived from human activities, are becoming more apparent â€“ air and water quality are increasingly compromised, oceans are being overfished, pests and diseases are extending beyond their historical boundaries, and deforestation is exacerbating flooding downstream. It has been reported that approximately 40-50% of Earthâ€™s ice-free land surface has been heavily transformed or degraded by anthropogenic activities, 66% of marine fisheries are either overexploited or at their limit, atmospheric CO2 has increased more than 30% since the advent of industrialization, and nearly 25% of Earthâ€™s bird species have gone extinct in the last two thousand years. Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.
A brief history
The simple notion of human dependence on Earthâ€™s ecosystems probably reaches to the start of our speciesâ€™ existence, when we benefited from the products of nature to nourish our bodies and for shelter from harsh climates. Recognition of how ecosystems could provide more complex services to mankind date back to at least Plato (c. 400 BC) who understood that deforestation could lead to soil erosion and the drying of springs. However, modern ideas of ecosystem services probably began with Marsh in 1864 when he challenged the idea that Earthâ€™s natural resources are not infinite by pointing out changes in soil fertility in the Mediterranean. Unfortunately, his observations and cautions passed largely unnoticed at the time and it was not until the late 1940s that societyâ€™s attention was again brought to the matter. During this era, three key authors â€“ Osborn, Vogt, and Leopold â€“ awakened and promoted recognition of human dependence on the environment with the idea of â€˜natural capitalâ€™. In 1956, Sears drew attention to the critical role of the ecosystem in processing wastes and recycling nutrients. An environmental science textbook called attention to â€œthe most subtle and dangerous threat to manâ€™s existenceâ€¦ the potential destruction, by manâ€™s own activities, of those ecological systems upon which the very existence of the human species dependsâ€�. The term â€˜environmental servicesâ€™ was finally introduced in a report of the Study of Critical Environmental Problems, which listed services including insect pollination, fisheries, climate regulation and flood control. In following years, variations of the term were used, but eventually â€˜ecosystem servicesâ€™ became the standard in scientific literature.
Modern expansions of the ecosystem services concept include socio-economic and conservation objectives, which are discussed below. For a more complete history of the concepts and terminology of ecosystem services, see Daily (1997).
Experts currently recognize four categories of ecosystem services. The following lists represent samples of each:
- Provisioning services
- â€¢ food (including seafood and game), crops, wild foods, and spices
- â€¢ water
- â€¢ pharmaceuticals, biochemicals, and industrial products
- â€¢ energy (hydropower, biomass fuels)
- Regulating services
- â€¢ carbon sequestration and climate regulation
- â€¢ waste decomposition and detoxification
- â€¢ purification of water and air
- â€¢ crop pollination
- â€¢ pest and disease control
- Supporting services
From Yahoo Answers
Answers:Ponds are nothing more than depressions in the ground where water collects. They are quiet, shallow bodies of water that allow enough sunlight to reach their bottom. The sunlight supports the growth of rooted plants from shore to shore. Some pond plants grow entirely underwater or have parts that extend above the surface. Leafy plants may float on the surface. Other plants can grow along the pond edge. If left alone, ponds will eventually fill in with dirt and debris until they become solid land. It often takes hundreds of years for a pond to be transformed from a body of clear water into soil. Ponds often support a large variety of animal and plant life. Wind and streams can carry in eggs, seeds, and organisms that develop into various life forms. Pond animals include birds, crayfish, fish, frogs, insects, and turtles. Microscopic organisms also thrive in most ponds. Water temperature of ponds is fairly even from top to bottom and changes with the outside air temperature. There is little wave action in the water body, and the pond bottom is usually mud-covered. The amount of dissolved oxygen in the pond may vary greatly during a day. In cold climates, the entire pond can freeze solid.
Answers:how will u set a pond on fire, well lets assume that for some reason u have gasoline on the surface of the pond, first the fire will kill all plants like algae etc and animals floating on the surface, if that is done u have a reduction in the population of such organisms aand as a result any other organism that feeds on those burnt out surface plants and animals will suffer and their population will reduce too or they might die off, so the chain continues and the ecosystem is now affected. ANother scenerio is that the fire might increase the temp of the pond and affect the dissolved oxygen or CO2 in the water this will also affect the well being of organisms in the pond, in extreme cases their might be no living organism left in the pond after a prolonged fire
Answers:A pond is a living ecosystem - a balance of fish, plants, and beneficial bacteria that compliment and support each other. When the ecosystem is balanced, a properly designed and built pond will require very little maintenance. A variety of natural, and fish friendly materials are available for those times when an adjustment is needed to keep the ecosystem in balance.
Answers:http://www.shamrockponds.com/ecosystem.htm http://images.search.yahoo.com/search/images?ei=UTF-8&p=pond%20ecosystem&fr=ieas&fr2=tab-web Hope this helps