Ecological Processes

• Primary producers include everything from microscopic plants of the oceans to the giant redwoods of California.
• Primary production is influenced by the availability of nutrients.
• If primary production declines, energy flow to higher trophic levels is diminished, potentially compromising the sustainability of animal populations dependent on plants for food.
• Too much primary production can also cause problems, such as when lakes experience an overload of nutrients. Such eutrophic conditions can alter the composition of animal and plant life and result in reduced oxygen levels as organic matter decomposes. The “dead zone” in the Gulf of Mexico is an example of the effects caused by excess nutrients and too much primary production.

• Many pesticides, chemicals used in industry, pollutants, and waste products can interfere with species reproduction, one of the most important ecological processes.
• Changes in land use that alter the extent and distribution of ecological systems can directly affect ecological processes in particular areas, often causing associated changes in primary production, nutrient cycling, and erosion and sediment transport. For example, changing forested land to urban or agricultural lands influence the amounts and types of primary producers, the infiltration of water into soils, and the storage and cycling of carbon and nutrients.
• Water quality management is affected by:
  • Activities that upset the balance between primary production and respiration (such as wastewater treatment plant discharge, nutrients from fertilizers and animal manure, and ultraviolet radiation).
  • Activities that affect sediment erosion and transport.

Only one indicator that meets the ROE criteria, Carbon Storage in Forests, is available to address this question because ecological processes are difficult to measure directly, particularly at a national scale.

Ecological processes such as primary production, respiration, energy, carbon and nutrient flow through food webs, reproduction, and decomposition are represented as rates of change, which requires repeated measurement over time. This is difficult to achieve for many ecosystems at a local scale and even more difficult at the national scale. For example, remote sensing imagery has been used to obtain "snapshots" of indicators of ecosystem conditions over time, and to infer ecological processes such as terrestrial net primary production.

The Normalized Difference Vegetation Index has been estimated at a national scale using remote sensing. Repeated measures over a season might provide an indicator of net primary production. Indicators for other ecological processes, such as respiration, nutrient cycling, or decomposition have been developed for ecosystems at watershed scales, but have not been developed at the national scale. Developing these indicators at the national scale represents a significant scientific and research challenge.