Consideration is being given to including a broad national overview of recreation in the 2001 Report. There is information on the number of beach closures more than 7,000 in 1998, indicating significant restrictions on recreational use due to water quality conditions. Productivity is generally inferred from other data rather than measured directly. Measures include the yield of harvested crops, tree growth, satellite measurements of plant growth, and amount of carbon stored in ecosystems. Nitrogen and phosphorous are key plant nutrients.
Excesses can contribute to ecosystem degradation, whereas deficiencies can hinder plant growth.
The accumulation of synthetic organic chemicals or abnormal levels of heavy metals can harm plants and animals and raise human health concerns. Data on their condition provide information about both the communities and their component species. Species have different ecological functions, levels of human interest, and preferences for different habitat. Measure address, for selected groups of native animal species, whether the group is secure or imperiled and whether its population is increasing, decreasing, or stable. Measures report on nonnative invasive species and outbreaks of parasitic insects, diseases, and other native species.