VI.8 Provisioning Services: A Focus on Fresh Water
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VI.8 Provisioning Services: A Focus on Fresh Water Margaret A. Palmer and David C. Richardson OUTLINE 1. Introduction 2. Freshwater ecosystem services and the processes that support them 3. Status of freshwater ecosystem services 4. The future of freshwater services Healthy freshwater ecosystems play crucial roles in the global environment by controlling fluxes of minerals, nutrients , and energy, and, by providing goods and services critical to humans including water for drinking or irrigation and fish for consumption. Freshwater ecosystems also provide regulating services such as carbon sequestration, flood control, and cultural services such as recreational fishing, swimming, or aesthetic enjoyment of the open water . These goods and services are all supported by underlying ecological processes (also called ecosystem functions) such as primary production, decomposition, and nutrient processing. The well-known and dramatic decline in freshwater biodiversity that has occurred in the last several decades has been accompanied by local and regional losses of freshwater ecosystem services. These losses are being driven largely by human activities. Ecosystem services cannot be restored once lost without a focus on the underlying ecological processes that support them, and, thus, a great deal of research is ongoing to understand and quantify the linkage between services and the rates of key ecological processes. GLOSSARY anaerobic. Absence of oxygen, also called anoxic (e.g., anaerobic sediments). chemotroph. An organism that makes its own food but, instead of using energy from the sun as photosynthetic organisms do, uses inorganic chemicals as an energy source; includes wetland bacteria called methanogens that produce methane (a greenhouse gas) by decomposing organic matter in anaerobic environments. denitrification. The microbial process that converts nitrate (NO3  , nutrient readily available to plants) to nitrite to free nitrogen gas (N2, generally unavailable to plants); requires a carbon source and an anaerobic environment. geomorphology. The study of the formation, alteration, and configuration of landforms and their relationship with underlying structures. hydrology. The study of the properties, distribution, and effects of water on the earth’s surface. hyporheic zone. The subsurface region under and lateral to a stream in which groundwater and surface water mix; considered metabolically important in streams and rivers. organic matter, particulate and dissolved. Derived from the degradation of dead organisms, plant or animal; particulate organic matter would include leaf pieces, wood, animal body parts, etc.; dissolved organic matter refers to organic molecules that are typically less than 0.7 mm; also called dissolved organic carbon . point- / non-point-source pollution. Point-source pollution comes from clearly identifiable local sources, includes outlet pipes from wastewater treatment plants or other industrial sources. Non-point-source pollution comes from many diffuse sources and is carried by rainfall or snowmelt as it moves over or through the ground to fresh water. These pollutants include excess fertilizers, herbicides from agricultural or residential areas, oils or other toxic chemicals from urban runoff, salt from roads or irrigation practices, bacteria or nutrients from livestock, pet waste, or pollutants from atmospheric deposition. primary and secondary production. The production of new living material through photosynthesis by autotrophs (e.g., plants, algae) is primary production ; tissue produced by heterotrophs (e.g., macrofauna , fish) is referred to as secondary production because these organisms rely on the consumption of living or dead organic material. recharge/discharge. Movement from surface water belowground into an aquifer ‘‘recharges’’ the aquifer , whereas movement from the groundwater back to surface water represents discharge from an aquifer. 1. INTRODUCTION Only about 3% of the world’s water is fresh water, and most of that is bound up in glaciers, underground aquifers, or ice pack. Yet the entire human population depends on fresh water for drinking and on the goods and services provided by freshwater ecosystems. In fact, since antiquity, humans have chosen to live and work near water bodies, and entire civilizations have developed along waterways. Today, most people rely on rivers and streams for their domestic water needs as well as for irrigation, energy, and recreation. They rely on wetlands and riparian buffers to purify water, mitigate the impacts of flooding, and support diverse assemblages of plants and wildlife. Healthy freshwater ecosystems also play crucial ecological roles globally by controlling fluxes of minerals, nutrients, and energy. Indeed, all ecosystems worldwide depend to some extent on freshwater ecosystems and the complex connections that exist among terrestrial flora and fauna, groundwater, surface waters, and water vapor (plate 20). Biodiversity and ecosystem processes in terrestrial, polar, and coastal ecosystems are all influenced by inputs of fresh water and fluxes...