(See: Daily, G. C. (Ed). 1997. Nature's Services: Societal Dependence on Natural Ecosystems. Island Press, Washington DC)

What is the scope of the sector? What issues should be included? Ecosystem services include a wide range of issues related to natural ecosystems which are highly regarded by society, and yet are often difficult to value economically. The sector includes the following issues:

• Storage of water, nitrogen, and other nutrients, including carbon
• Mitigation of floods and droughts and moderation of winds and waves
• Air and water purification
• Generation and renewal of soil and soil fertility
• Pollination and seed dispersal for crops and natural vegetation
• Control of agricultural pests
• Preservation of resources in national parks, monuments, and wilderness areas
• Wildlife refuges/habitat for non-game species and habitat for game fish, birds, and mammals
• Protection of endangered species
• Maintenance of biological diversity to preserve genetic resources, protect long-term ecosystems viability, and assure potential for agricultural, medical, and industrial discoveries
• Recreational opportunities, spiritual or aesthetic enjoyment of nature, and ethical issues of preserving natural and pristine areas.

What are overlaps and synergies with other sectors? There are many synergies with almost all of the other sectors. The Forestry sector focuses on one major ecosystem product, namely wood and wood products; further, forests comprise an important type of natural ecosystem. There are also synergies with the food availability sector mainly through providing wild fisheries breeding areas. Additionally there will be links with the water sector because natural ecosystems from which the ecosystem services are derived include water ecosystems of lakes, streams, and oceans. Water is a critical component of all ecosystems. There may be synergies through human health through a variety of mechanisms including pollen production, pollution dissipation, and vector breeding grounds (for vector-borne diseases). Biomass fuels for energy may be derived from natural products extracted from ecosystems.

What are the key current and expected future (non-climatic) stresses on ecosystems? Current stresses that are expected to be amplified in the future include:

• Land use changes and habitat fragmentation
• Chronic pollution, both air and water
• Introduction of invasive and exotic species
• Over-exploitation of our highly-prized natural areas such as National Parks

How will climate change and variability exacerbate or ameliorate these stressors? What new stresses might be introduced? Climate change will impact natural ecosystems through warming temperatures, and shifting patterns of precipitation; these shifts in climatic conditions will cause many ecosystems to shift or "migrate" northward to higher in elevation in response to the shifted climate. However, because many boundaries of nature preserves and National Parks are fixed, the particular protected ecosystems may no longer exist within the defined and fixed boundaries. For example, Saguaro National Park may have to be renamed if the famous cactus moves outside of the Park boundaries. High alpine ecosystems which are already at the tops of mountain ranges will have no where to migrate. Developed urban areas will likely act as barriers to migration as well. Warmer climate has already led to the substantial melting of alpine glaciers (which act as major water storage facilities). For example 73% of the some glaciers in Glacier National Park have already melted; within about the next 50 years, this National Park may also have to be re-named as all glaciers may melt by then. Altered patterns and forms of precipitation (rain vs. snow) will also impact ecosystems through altered patterns of water supply.

What are the most important information needs? There is relatively little information on the impacts of climate change on natural ecosystems. While there may be studies of impacts on individual species, there are very few studies on whole ecosystem responses to climate change. There is also only limited information on potential adaptation of natural ecosystems. Additionally, recent research has begun to explore economic valuation of ecosystem services; this work needs to advance for the full impacts of climate change to be valued. A brief list of some of the information needs includes:

• Which ecosystems supply what services?
• What is the impact of various human activities upon the supply of services?
• What are the relationships between quantity or quality of services and the condition of the ecosystem supplying them?
• To what extent do the services depend on biodiversity?
• To what extent have various services already been impaired? How are these impairments distributed geographically?
• How interdependent are the services? How does exploitation influence functioning?
• To what extent and over what time scale are the services amenable to repair?
• How effectively, and at how large a scale, can existing human technology substitute for ecosystem services?
• What proportion and spatial pattern of land must remain relatively undisturbed, locally, regionally, and globally, to sustain the delivery of ecosystem services?

What coping strategies might be available to reduce climatic and other stresses? The primary coping strategy for ecological systems is to reduce chronic pollution in both air and water and other stresses that lead to "biotic impoverishment". Maintaining ecosystem structure is critical to maintaining its function.