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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 like the Decomposition of wastes. Ecosystem services are distinct from other ecosystem products and functions because there is human demand for these natural assets. Services can be subdivided into five 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; ''cultural'', such as spiritual and recreational benefits; and ''preserving'', which includes guarding against uncertainty through the maintenance of diversity. As human populations grow, so do the resource demand imposed on ecosystems and the impacts of our global footprint. Many people have been plagued with the misconception that these ecosystem services are free, invulnerable and infinitely available. However, the impacts of Anthropogenic use and abuse are becoming evermore apparent – air and water quality are increasingly compromised, oceans are being over-fished, pests and diseases are extending beyond their historical boundaries, Deforestation is eliminating flood control around human settlements. It has been reported that approximately 40-50% of Earth’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 Earth’s bird species have gone extinct in the last two thousand years Vitousek, P.M., J. Lubchenco, H.A. Mooney, J. Melillo. 1997. Human domination of Earth’s ecosystems. Science 277: 494-499.. Consequently, society is coming to realize that ecosystem services are not only threatened and limited, but that the pressure to evaluate trade-offs between immediate and long-term human needs is urgent. To help inform decision-makers, economic value is increasingly associated with many ecosystem services and often based on the cost of replacement with anthropogenically-driven alternatives. The on-going challenge of prescribing economic value to nature is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species. __TOC__ A BRIEF HISTORY The simple notion of human dependence on Earth’s ecosystems probably reaches to the start of our species’ existence, when as hunter-gatherers we benefited from the products of nature to nourish our bodies and the habitats that provided shelter from harsh climates. Recognition of how ecosystems could provide even more complex services to humankind date back to at least , Fisheries , Climate regulation and Flood control. In following years, variations of the term were applied but eventually ‘ecosystem services’ became the standard among scientific literature Ehrlich, P.R. and A. Ehrlich. 1981. Extinction: The Causes and Consequences of the Disappearance of Species. Random House, New York. 305pp.. Modern expansions of the ecosystem services concept have come to encompass Socio-economic and Conservation objectives, which are discussed below. For a more complete history of the concepts and terminology surrounding ecosystem services, see Daily (1997). EXAMPLES Experts currently recognize five categories of ecosystem services Daily, G.C. 2000. Management objectives for the protection of ecosystem services. Environmental Science & Policy 3: 333-339.Millennium Ecosystem Assessment (MEA). 2005. Ecosystems and Human Well-Being: Synthesis. Island Press, Washington. 155pp.. The following lists represent samples of each: : ''Provisioning services'' ::• foods (including seafood and game) and spices ::• precursors to pharmaceutical and industrial products ::• Energy ( Hydropower , Biomass Fuels ) : ''Regulating services'' ::• Carbon Sequestration and Climate regulation ::• waste Decomposition and detoxification ::• nutrient dispersal and cycling : ''Supporting services'' ::• purification of water and air ::• crop Pollination and seed Dispersal ::• Pest and disease control : ''Cultural services'' ::• cultural, intellectual and spiritual inspiration ::• recreational experiences (including Ecotourism ) ::• scientific discovery : ''Preserving services'' ::• genetic and Species Diversity for future use ::• accounting for uncertainty ::• protection of options To understand the relationships between humans and natural ecosystems through the services derived from them, consider the following cases: :• In New York City, where the quality of drinking water had fallen below standards required by the U.S. Environmental Protection Agency (EPA), authorities opted to restore the polluted Catskill Watershed that had previously provided the city with the ecosystem service of water purification. Once the input of sewage and pesticides to the Watershed area was reduced, natural abiotic processes such as soil adsorption and filtration of chemicals, together with biotic recycling via root systems and soil microorganisms, water quality improved to levels that met government standards. The cost of this investment in natural capital was estimated between $1-1.5 billion, which contrasted dramatically with the estimated $6-8 billion cost of constructing a water filtration plant plus the $300 million annual running costs Chichilnisky, G. and G. Heal. 1998. Economic returns from the biosphere. Nature 391: 629-630.. :• and oak-woodland habitat available for wild bees within 1-2 km of a farm can strongly stabilize and enhance the provision of pollination services, thereby providing a potential insurance policy for farmers of this region. :• In watersheds of the Yangtze River (China), spatial models for water flow through different forest habitats were created to determine potential contributions for Hydroelectric Power in the region. By quantifying the relative value of ecological parameters (vegetation-soil-slope complexes), researchers were able to estimate the annual economic benefit of maintaining forests in the watershed for power services to be 2.2 times that if it were harvested once for Timber Guo, Z.W., X.M. Xio and D.M. Li. 2000. An assessment of ecosystem services: water flow regulation and hydroelectric power production. Ecological Applications 10: 925-936.. ECOLOGY Understanding of ecosystem services requires a strong foundation in Ecology , which describes the underlying principles and interactions of organisms and the Environment . Since the scales at which these entities interact can vary from Microbes to Landscapes , milliseconds to millions of years, one of the greatest remaining challenges is the descriptive characterization of energy and material flow between them. For example, the area of a forest floor, the Detritus upon it, the microorganisms in the soil and characteristics of the soil itself will all contribute to the abilities of that forest for providing ecosystem services like carbon sequestration, water purification, and Erosion prevention to other areas within the Watershed . Note that it is often possible for multiple services to be bundled together and when benefits of targeted objectives are secured, there may also be ancillary benefits – the same forest may provide Habitat for other organisms as well as human recreation, which are also ecosystem services. The complexity of Earth’s ecosystems poses a challenge for scientists as they try to understand how relationships are interwoven among organisms, processes and their surroundings. As it relates to human ecology, a suggested research agenda for the study of ecosystem services includes the following steps: :1. identification of ''ecosystem service providers'' (''ESP''s) – Species or populations that provide specific ecosystem services – and characterization their functional roles and relationships; :2. determination of community structure aspects that influence how ESPs function in their natural Landscape , such as compensatory responses that stabilize function and non-random extinction sequences which can erode it; :3. assessment of key environmental ( Abiotic ) factors influencing the provision of services; :4. measurement of the spatial and temporal scales ESPs and their services operate on. Recently, a technique has been developed to improve and standardize the evaluation of ESP functionality by quantifying the relative importance of different species in terms of their efficiency and abundance Balvanera, P. C. Kremen, and M. Martinez. 2005. Applying community structure analysis to ecosystem function: examples from pollination and carbon storage. Ecological Applications 15: 360-375.. Such parameters provide indications of how species respond to changes in the environment (i.e. predators, resource availability, climate) and are useful for identifying species that are disproportionately important at providing ecosystem services. However, a critical drawback is that the technique does not account for the effects of interactions, which are often both complex and fundamental in maintaining an ecosystem and can involve species that are not readily detected as a priority. Even so, estimating the functional structure of an ecosystem and combining it with information about individual species traits can help us understand the Resilience of an ecosystem amidst environmental change. Ecosystem Function and Biodiversity Many ecologists also believe that the provision of ecosystem services can be stabilized with biodiversity. Also with increased biodiversity there would be a greater variety of different types of ecosystem services available to society.The link between biodiversity, species richness, and ecosystem stability is important to understand to be able to know how to conserve resources, as well as to create designs to utilize these resources. The Redundancy and Rivet Hypotheses The redundancy (sometimes referred to as the Functional Compensation) and rivet hypotheses seek to explain how an ecosystem functions, based on the ecological role of organisms within it. The redundancy and rivet hypotheses are the most commonly used explanations for the link between Ecosystem Function and its Biodiversity , but others included the “idiosyncratic” and the “null” hypothesis.Lawton, John H. “What do species Do in Ecosystems?”, Oikos, Dec 1994.vol71,no.3,pp368. Nordic Society Oikos The redundancy hypothesis states that there are more than one species that share the same function in an ecosystem, thus each species' performance in the ecosystem is “redundant”Walker, Brian H.. "Biodiversity and ecological redundancy." Conservation Biology Vol.6, no.1March 1992 18-23. 29 May 2007 Species Redundancy and Ecosystem ReliabilityConservation Biology 12 (1), 39–45.doi:10.1046/j.1523-1739.1998.96379.x.. In the rivet hypothesis,(sometimes called "rivet popping") proposed by Paul Ehrich, “all species make a contribution to ecosystem performance.”Lawton, John H. “What do species Do in Ecosystems?”, Oikos, Dec 1994.vol71,no.3,pp368. Nordic Society Oikos The main difference between these theories is the rate at which the loss of species affects the function of the ecosystems. The rates of these theories can be illustrated with statistical models. In the redundancy model the function of the ecosystem decreases slowly with every species lost, while in the rivet model ecosystem function decreases rapidly. |
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