VI.8 Provisioning Services: A Focus on Fresh Water Margaret A. Palmer and David C. Richardson OUTLINE methanogens that produce methane (a greenhouse gas) by decomposing organic matter in anaerobic 1. Introduction environments. 2. Freshwater ecosystem services and the processes denitrification. The microbial process that converts that support them nitrate (NOÀ, nutrient readily available to plants) to 3. Status of freshwater ecosystem services 3 nitrite to free nitrogen gas (N , generally unavail- 4. The future of freshwater services 2 able to plants); requires a carbon source and an anaerobic environment. Healthy freshwater ecosystems play crucial roles in the geomorphology. The study of the formation, alteration, global environment by controlling fluxes of minerals, nu- and configuration of landforms and their relation- trients, and energy, and, by providing goods and services ship with underlying structures. critical to humans including water for drinking or irrigation hydrology. The study of the properties, distribution, and fish for consumption. Freshwater ecosystems also and effects of water on the earth’s surface. provide regulating services such as carbon sequestration, hyporheic zone. The subsurface region under and lat- flood control, and cultural services such as recreational eral to a stream in which groundwater and surface fishing, swimming, or aesthetic enjoyment of the open wa- water mix; considered metabolically important in ter. These goods and services are all supported by under- streams and rivers. lying ecological processes (also called ecosystem functions) organic matter, particulate and dissolved. Derived from such as primary production, decomposition, and nutrient the degradation of dead organisms, plant or animal; processing. The well-known and dramatic decline in fresh- particulate organic matter would include leaf pieces, water biodiversity that has occurred in the last several de- wood, animal body parts, etc.; dissolved organic cades has been accompanied by local and regional losses matter refers to organic molecules that are typically of freshwater ecosystem services. These losses are being less than 0.7 mm; also called dissolved organic car- driven largely by human activities. Ecosystem services bon. cannot be restored once lost without a focus on the under- point- / non-point-source pollution. Point-source pollu- lying ecological processes that support them, and, thus, a tion comes from clearly identifiable local sources, in- great deal of research is ongoing to understand and quantify cludes outlet pipes from wastewater treatment plants the linkage between services and the rates of key ecological or other industrial sources. Non-point-source pollu- processes. tion 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 GLOSSARY excess fertilizers, herbicides from agricultural or res- anaerobic. Absence of oxygen, also called anoxic (e.g., idential areas, oils or other toxic chemicals from anaerobic sediments). urban runoff, salt from roads or irrigation practices, chemotroph. An organism that makes its own food but, bacteria or nutrients from livestock, pet waste, or instead of using energy from the sun as photosyn- pollutants from atmospheric deposition. thetic organisms do, uses inorganic chemicals as primary and secondary production. The production an energy source; includes wetland bacteria called of new living material through photosynthesis by 626 Ecosystem Services autotrophs (e.g., plants, algae) is primary produc- groundwater, surface waters, and water vapor (plate tion; tissue produced by heterotrophs (e.g., macro- 20). Biodiversity and ecosystem processes in terrestrial, fauna, fish) is referred to as secondary production polar, and coastal ecosystems are all influenced by in- because these organisms rely on the consumption of puts of fresh water and fluxes of organic matter and living or dead organic material. other materials from rivers and streams. recharge/discharge. Movement from surface water As outlined in earlier chapters in this section (chap- belowground into an aquifer ‘‘recharges’’ the aqui- ters VI.1 and VI.2), ecosystem services can be cate- fer, whereas movement from the groundwater gorized as provisioning, regulating, or cultural. Pro- back to surface water represents discharge from an visioning services are those ‘‘products’’ obtained from aquifer. ecosystems such as fish for consumption or water for drinking or irrigation. Regulating services include nonmaterial benefits that humans receive from eco- 1. INTRODUCTION systems such as water purification, carbon sequestra- Only about 3% of the world’s water is fresh water, and tion, or flood control. Cultural services represent non- most of that is bound up in glaciers, underground material benefits as well, such as recreational fishing, aquifers, or ice pack. Yet the entire human population swimming, or aesthetic enjoyment of the open water, depends on fresh water for drinking and on the goods but we choose to focus on provisioning and regulat- and services provided by freshwater ecosystems. In fact, ing services in this chapter. As we describe below, since antiquity, humans have chosen to live and work each provisioning and regulating service is supported near water bodies, and entire civilizations have devel- by underlying ecological processes (figure 1). In some oped along waterways. Today, most people rely on cases, just a few processes may support a service, and in rivers and streams for their domestic water needs as other cases, a whole suite of complex processes interact well as for irrigation, energy, and recreation. They rely to provide the basis for a service. For example, water on wetlands and riparian buffers to purify water, mit- purification may rely on the ecological processes of igate the impacts of flooding, and support diverse as- denitrification, decomposition of organic matter, and semblages of plants and wildlife. Healthy freshwater algal photosynthesis, whereas riverine flood control ecosystems also play crucial ecological roles globally may depend almost exclusively on the presence of by controlling fluxes of minerals, nutrients, and energy. healthy (intact) floodplains. Species also rely on eco- Indeed, all ecosystems worldwide depend to some ex- system services to provide them with food, optimal tent on freshwater ecosystems and the complex con- conditions for reproduction, and dispersal routes, to nections that exist among terrestrial flora and fauna, name a few. Underlying ecological processes Photo- & Sediment Hydrologic Organic Nutrient supply & matter processing chemo- transport regime processing synthesis Provisioning services Regulating services • Biodiversity • Biodiversity • Water supply • Water purification • Food production • Carbon and nitrogen sequestration • Flood control • Erosion control • Temperature regulation • Recreation Figure 1. Examples of basic ecological processes that support the cessing) are described in table 1. Provisioning services are prod- services provided by freshwater ecosystems. Subcategories of ucts obtained from ecosystems, whereas regulating services in- processes (e.g., denitrification as one component of nutrient pro- clude nonmaterial benefits. Provisioning Services 627 Because freshwater ecosystems are extremely di- encing the underlying process. For example, if people verse, as are the services they support, we begin with a want abundant trout fisheries in a region, they may brief description of the major types of ecosystems stock rivers with hatchery-reared juveniles (effec- and then move into a detailed discussion of the services tively enhancing the ‘‘fish reproduction/recruitment they provide. process’’), which may in turn lead to a decline in the productivity of other fish species because of competi- Wetland ecosystems: Any ecosystem that is tion for food. Even the act of meeting basic human regularly, but not necessarily continuously, satu- needs such as providing warmth for people in cold rated by precipitation, surface water, or ground- winter months can enhance the provisioning of one water and is occupied by vegetation that is service (heat production from burning wood) at the adapted to saturated conditions; includes bogs, expense of another (carbon sequestration in living trees swamps, fens, and tidal or nontidal freshwater that provide wood resource). marshes. There is a great deal of active research now to iden- Running-water ecosystems: Any ecosystem with tify ways to measure ecosystem services by quantifying flowing water that is a low point in the landscape their linkage to the rates of the underlying ecological where water drains, especially after rain; peren- processes. The motivation to measure ecosystem ser- nial streams flow most of the year through well- vices comes in part from recognizing that in any coupled defined channels; intermittent streams flow only social–ecological system, there will always be trade-offs part of the year; and ephemeral streams flow only that need to be balanced, with potential needs for com- after major rain events; however, hyporheic flow, pensation if something valuable is lost. Take, for ex- which is not readily visible, may persist. Running- ample, extractive mining that can reduce water quality. water ecosystems include rivers, streams, creeks, Communities may find they need to engage in extractive and brooks. mining as a source of income; they may partially com- Lake, pond, and reservoir ecosystems: Any body pensate for the degradation