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 (NO, 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 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 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 ‘‘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, , 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 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 ecosystems: Any body pensate for the degradation in water quality at that site of water filling a depression in the landscape that by enhancing water purification at other points in the may have been formed in a variety of ways in- watershed. A second example might be reforestation cluding glacial retreat, tectonic events, river around housing developments; the forests lost when overflows or meanders, and natural damming of houses were built are reestablished to provide oppor- running waters (e.g., beaver ponds); their outflow tunities for recreation. No single patch can provide may feed streams and rivers. the full suite of services residents might want, but Glaciers and ice pack ecosystems: Any body of ice landscape-level management can provide a bundle of on a mountaintop or in polar regions where snow services that contribute to human well-being. accumulation exceeds or equals melting; these are The motivation to link the rates of ecological pro- slowly moving or have moved at one point in cesses to ecosystem services follows directly from the time; once believed to be barren but now known need or desire to enhance or restore a service that has to harbor diverse flora and fauna. been lost or degraded. Services cannot be restored without a focus on the underlying ecological processes that support them. For example, denitrification, an eco- logical process that contributes to the 2. FRESHWATER ECOSYSTEM SERVICES of water purification, occurs in many freshwater eco- AND THE PROCESSES THAT SUPPORT THEM systems (table 1), but knowledge of the rate of nitrogen Healthy fresh waters are living, functional systems. removal is necessary to estimate whether denitrifica- Valuable ecosystem services that they support include tion improves water quality. Many surrogate metrics for water storage and supply, the purification of water system performance have been used in assessments of through the removal of excessive nutrients, contami- freshwater ecosystems (e.g., plant biomass, sediment nants, and sediments, carbon and nitrogen sequestra- carbon content); however, to date, there is no published tion, food production in the form of invertebrates and work in which such surrogates have been directly linked fish, support of biodiversity in aquatic and nearby to the rate of a specific ecological process and, therefore, terrestrial habitats, flood control, and recreation (table to the magnitude of impact on ecosystem service. Thus, 1). Each service is supported by one or more ecological an extremely active area of research is now concerned processes (figure 1) that, if lost, could lead to degra- with how to quantify these services, the spatial and dation of that service. Societal preferences can lead to temporal variability of these services across and within choices that enhance one service at the loss or decline different biomes, and the potential use of valid surrogates of another, and this is often accomplished by influ- for measuring the underlying process rates that are less Table 1. Rivers and streams provide a number of goods and services that are critical to their health and provide benefits to society; the major services are outlined along with the ecological processes that support the function, how it is measured, and why it is important.

Consequences of Supporting Measurements Ecosystem/ Ecosystem service losing the service ecological process required habitat

Water purification Nutrient processing Excess nutrients (eutrophication) Retention, storage, and Direct measures of rates Riparian zone, river and can build up in the water, transformation of of transformation of streambeds, wetlands, making it unsuitable for excess nitrogen and nutrients; e.g., lake littoral zones drinking or supporting phosphorus; decomposition denitrification life; in particular, algal of organic matter (production of N2 blooms resulting from gas, conversion of excess nutrients can lead NO3 to more usable to anoxic conditions N forms); decomposition and death of biota measured as rate of organic matter loss over time Processing of Toxic contaminants kill biota; Biological removal by plants Direct measures of Riparian zone and contaminants excess sediments smother and microbes of materials contaminant uptake or wetland and invertebrates, foul the gills such as excess sediments, changes in plants; bottom of fish, etc.; water not potable heavy metals, contaminants, etc. contaminant flux sediments of rivers, lakes, and wetlands

Water supply Loss of clean water supply Transport of clean water Measures of water Lakes, rivers, streams for residential, commercial, throughout watersheds movement, flow patterns, and urban use, irrigation pollution load supply for

Flood control Without the benefits of Slowing of water flow Measure stream and river , wetlands, floodplains, healthy from land to freshwater body discharge responses riparian zones stream corridor, and so flood frequency and to rain events watershed vegetation, magnitude reduced; increased flood frequency intact floodplains and and flood magnitude riparian vegetation buffer increases in discharge Infiltration Lost groundwater storage Intact floodplain, riparian, Infiltration of water Wetlands, streams, for private and public wetland vegetation increase in soils, water table floodplains use; vegetation and infiltration of rainwater levels in deep and biota suffer; increased and increase aquifer recharge shallow wells flooding in streams Carbon sequestration Primary production Water and atmospheric levels Aquatic plants and algae remove Measure rate of Freshwater ecosystems of CO2 build up, contributing CO2 from the water or photosynthesis typically with sunlight but to global warming atmosphere, convert this into based on loss of CO2 or particularly shallow biomass, thereby storing carbon production of O2 water habitats such as wetlands or midorder streams Secondary Water and atmospheric levels Production of biomass by Biomass accumulation All freshwater production of CO2 build up, contributing microbes and metazoans over time or measures ecosystems but to global warming stores carbon until their death of consumption, particularly the decomposition, or bottom sediments for chemotrophy microbes

Nitrogen sequestration Primary production Secondary production Creation of plant or animal For primary production, All freshwater and secondary supports fish and wildlife tissue over time measure the rate of ecosystems production photosynthesis in the and habitats stream; for secondary, measure growth rate of organisms Food production Primary production Reduction in food and food Production of new plant tissue Measure rate of All freshwater ecosystems products derived from aquatic photosynthesis typically and habitats with plants such as algae, rice, based on loss of CO2 sunlight but particularly watercress, etc. or production of O2 shallow water Decreased production (secondary) by habitats such as those consumers who rely on wetlands primary production as a food source Secondary Reduction in fisheries including Production of new animal Measure biomass changes All freshwater production finfish, crustaceans, shellfish, and tissue or microbial biomass over time or use ecosystems and habitats other invertebrates measures of fisheries harvest but particularly the water column and surficial sediments

Biodiversity Loss of aesthetic features, Diverse freshwater habitats, Identification of species, All ecosystem and impacts aquarium trade, watersheds in native functional groups habitat types but potential destabilization of vegetation, complex ecological or food webs particularly wetlands food web, loss of keystone communities support for plants and rivers species can impact water quality multiple trophic levels for fish (Continued) Table 1. (cont.)

Consequences of Supporting Measurements Ecosystem/ Ecosystem service losing the service ecological process required habitat

Temperature regulation If infiltration or shading is Water temperature is ‘‘buffered’’ Measure the rate of Shallow water habitats, reduced (as a result of if there is sufficient soil change in water especially wetlands clearing of vegetation infiltration in the watershed; temperature as air along stream), stream shading vegetation keeps temperature changes or water heats up beyond the water cool; water has a as increases in what biota are capable high heat capacity discharge occur of tolerating which stores excess heat

Erosion/sediment control Aquatic habitat burial Intact riparian vegetation and Flood-related sediment Wetlands, streams, and impacts fisheries, decreases minimization of overland flow movement rivers biodiversity, increases contaminant transport; reduction in downstream lake or reservoir storage volume

Recreation/tourism/ cultural, religious, or inspirational values Lost opportunities for people Clean water, particularly Time spent using Lakes, rivers, streams to relax, spend time with water bodies with pleasant resource recreationally; family; economic losses to natural surroundings such revenue generated from various industries, particularly as forests, natural wildlife boats, tourist attractions, tourist-oriented ones refuges, or natural wonders hotels Provisioning Services 631 time consuming than direct measurements of the process Climate change is bringing major challenges in some rates themselves. parts of the world as the freshwater ecosystem services Most of the ecological processes that support fresh- are being impacted by increasing water temperatures, water ecosystem services are themselves influenced by more precipitation in some areas, more droughts in underlying hydrologic and geomorphic processes such other areas, and in many regions more intense storms. as the flux of water and the supply (and transport) of In arid regions, the extraction of surface water and sediment. There is now abundant scientific evidence that groundwater is so severe that some major rivers no hydrologic interactions including groundwater/surface longer flow to the sea year round, and local commu- water interactions, the timing of low and high flows (or nities regularly experience water shortages. Today, the water cover), and the magnitude of flows in running- Colorado River is often a dry stream at its mouth in water systems or the period of inundation drive many Mexico because of damming, irrigation, and use for ecological and biogeochemical processes. in the southwestern United States. The Yellow River, in China, now ends hundreds of miles from its historical mouth because of the diversion of 3. STATUS OF FRESHWATER ECOSYSTEM SERVICES water for irrigation and drinking. People have been Freshwater ecosystems are among the most impacted forced to move from the watersheds because of periods ecosystems on earth. In most industrialized countries in of drought and flash floods. In wet regions, rivers and the world, extensive loss of wetlands and riparian eco- wetlands have a natural ability to absorb disturbances systems has already occurred, and the remaining habi- such as those associated with floods, but this buffering tats continue to be under threat. Degradation of lakes has been lost in many areas because of the diversion of and streams is also extremely common worldwide. The surface water and development in the watershed. In U.S. Environmental Protection Agency reported in 2000 urban watersheds, removing vegetation and soil and that more than one-third of fresh water in the United replacing them with impervious surfaces lead to higher States is officially listed as impaired or polluted. peak discharge and greater volume and frequency of Worldwide, over half of all wetlands have been altered, floods than in rural or forested streams. and over 1.3 billion people lack access to an adequate Freshwater ecosystems near developed (urban, supply of safe water. suburban, or residential) or agricultural areas have lost Major pollutants in freshwater ecosystems include many ecosystem services because of runoff from the excessive sediment, fertilizers, herbicides, pesticides, land, storm drains, sewers, and municipal point harmful pathogens, and industrial by-products such as sources. Urban areas occupy only a small fraction of heavy metals or PCBs. Agriculture is the source of 60% the U.S. land base, but the intensity of their impacts on of all pollution in U.S. lakes and rivers, and in Europe, local rivers can match that of agriculture. The imper- municipal and industrial sources contribute pollut- vious parking areas and rooftops that are associated ant loads to lakes and rivers. In developing countries, with urban centers, and poorly managed or tiled agri- industrialization and population growth will yield in- cultural fields, have reduced infiltration capacity and creasing pollution loads from both agricultural and in- lowered aquifer recharge. This, along with channeli- dustrial sources, but there are few data and little mon- zation of stream networks, has led to lower water ta- itoring from those freshwater ecosystems. Excessive bles and lake levels and to more intense flooding in nutrients (e.g., nitrogen and phosphorus needed for streams. Wetlands and all associated services are often plant growth) are the leading pollution problem for lost entirely because wetlands are being drained and lakes and the third most important pollution source for converted to agriculture, residential, or urban lands, rivers in the United States. The nutrient load generates lost as a result of road or highway construction, or algal blooms, which can spoil drinking water, make stripped to harvest construction materials. recreational areas unpleasant, and contain harmful Dudgeon and colleagues grouped the major stressors toxins or pathogens. The eventual decomposition of the on freshwater ecosystems into five categories (figure 2), algal bloom creates anaerobic conditions in the water and it is now well accepted that the combination of these that can kill fish and other aquatic organisms. Heavy stressors has led to very high extinction rates for fresh- metals and other industrial by-products can enter the water species. In fact, extinction rates of freshwater aquatic food web and accumulate in organisms, in- fauna are estimated to be at least five times higher than cluding those harvested for human consumption. Ac- those of terrestrial or avian species. Around the world, cording to the U.S. Environmental Protection Agency, we are losing fish, amphibian, and macroinvertebrate statewide advisories for freshwater fish warn of con- species at alarming rates. For example, overfishing, centrations of pollutants, namely mercury and PCBs, at construction, water diversion, and pollution have led to levels of human health concern. the severe decline of commercial and recreational fish 632 Ecosystem Services

Modified lands, and lakes that are typically sustained by an ex- Habitat tended period of snowmelt will be reduced. loss or flows or degradation water The management responses that are needed to pro- extractions tect freshwater ecosystems vary depending on water stress (use-to-availability ratio), land use, how exten- sively runoff events change relative to current patterns, and needs of people within the watershed. In general, society will have to continue to stress many freshwater ecosystems in order to provide water for irrigation and Nonnative Pollution species urban populations, among other things. In fact, some ecosystem services will continue to be lost because a positive benefit is derived from the activities introducing Over- the stress, such as water diversion for human use and exploitation crops, infrastructure in the watershed that provides housing or industry, or energy from hydroelectric . As indicated earlier, other freshwater systems may need Figure 2. Five major categories of impacts that threaten fresh- to be preserved or restored to provide water purifi- water biodiversity and ultimately other ecosystem services. (Mod- ified from Dudgeon et al., 2006) cation, habitat for important aquatic species, or op- portunities for recreation. A balance has to be achieved between those services humans receive from converting or stressing freshwater systems and the benefits they species, such as the American shad in the Hudson and receive when those systems are left relatively intact. Delaware rivers or Chinese paddlefish in the Yangtze Management decisions need to take into account the River. full range of costs and benefits of provisioning, regu- lating, and cultural services. Provisioning services, such as fisheries harvest, have a market value and identifi- 4. THE FUTURE OF FRESHWATER SERVICES able profits and tend to drive decisions about con- Among the greatest challenges that face many nations verting freshwater systems. However, regulating and worldwide are how to sustain, restore, or judiciously cultural services are often overlooked because their manage the services that freshwater ecosystems pro- values are harder to define with no explicit market and vide and how to meet human demand for fresh water. diffuse societal benefits. Although a return to pristine, Practices that ensure enough water for drinking and precolonial freshwater ecosystems is clearly unrealistic irrigation have received the most attention. In some in the world today, the best management decisions will rapidly developing countries, such as India and China, be made when there is an adequate understanding of all industrial water demands are beginning to increase, ecosystem services and estimations of their material and agricultural and domestic needs from growing and nonmaterial values. populations continue to stress water resources. These When the goal is to restore or protect a freshwater problems will be exacerbated in areas that are expected ecosystem, a sensible approach is to take proactive to have less water with global climate change, such as measures to enhance or restore resilience and resistance southern Africa, central and northern South America, because this approach may also lead to environmental the Middle East, and parts of China. benefits such as increased water quality and restored Urbanization and climate change, both increasing fish and plant populations. Palmer and colleagues have with population growth, can have negative synergistic outlined examples of such measures including storm- effects; freshwater ecosystems, particularly in urban water management in developed basins or, even better, watersheds that receive more precipitation or have more land acquisition around freshwater bodies and riparian intense storms, will be hard pressed to provide ecosys- corridors to eliminate infrastructure in wetlands and tem services. In areas with snowpack, earlier snowmelt floodplains and allow regrowth of vegetation. If such caused by warmer temperatures may lead to massive actions are not taken, we will be left reacting to dam- flooding if the melting coincides with late winter or early ages and loss of ecosystem services. Some services may rains. In these regions, erosion of stream banks be replaceable by technology (e.g., water purification and loss of entire wetlands may occur. Lakes may ex- facilities, levees), but such measures could be extremely perience greater stress from sediment inputs, and, if they expensive and only tenable on fairly small scales. are in urban watersheds, contaminant inputs may also Protection of freshwater ecosystem services remains increase following rains. Summer flows to rivers, wet- a major challenge because it requires preservation, Provisioning Services 633 conservation, and management of freshwater ecosys- Baron, J. S., N. L. Poff, P. L. Angermeier, C. N. Dahm, P. H. tems and their surrounding watersheds. Future re- Gleick, N.G. Hairston Jr., R. B. Jackson, C. A. Johnston, search is needed to understand rates and variability B. D. Richter, and A. D. Steinman. 2002. Meeting eco- of ecosystem processes and how those processes influ- logical and societal needs for fresh water. Ecological Ap- ence ecosystem services. These measurements will al- plications 12: 1247–1260 Dudgeon, D., A. Arthington, M. O. Gessner, Z. Kawabata, D. low scientists to make better forecasts about how J. Knowler, C. Le´veˆque, R. J. Naiman, A. Prieur-Richard, freshwater ecosystem services will change with global D. Soto, M.L.J. Stiassny, and C. A. Sullivan. 2006. climate change, modifications in land use, and other Freshwater biodiversity: Importance, threats, status and future stresses. Finally, the scientific research commu- conservation challenges. Biological Reviews 81: 163–182. nity; public stakeholders; and management at local, EPA. 2000. National water quality inventory. EPA Publica- state, and national levels must work together to ensure tion 841-R-02-001, Washington, DC: EPA. the sustainability of freshwater ecosystem services. Mitsch, W. 2007. Wetlands. 4th ed. New York: John Wiley & Sons. Naiman, R., H. Decamps, and M. E. McClain. 2005. Riparia. FURTHER READING San Diego, CA: Elsevier Academic Press. Wetzel, R. G. 2001. Lake and River Ecosystems. San Diego: Allan, J. D., and M. M. Castillo. 2007. Stream Ecology, 2nd Academic Press. ed. Berlin: Springer.