Environmental Degradation (NS Lecture 11 September 2002)
Nancy Nicholson
Definitions of Environmental Degradation
The formal definition is arrived at by conferences involving different disciplines. The definitions reflect discussions about data and compromises concerning the effects of monitoring or enforcing various definitions. "Degradation" as a concept invokes the ecological concept of "carrying capacity." Carrying capacity is the ability of an environment to sustain the resource demands of a species or a community without losing its ability to regenerate the resource. Degradation usually means that carrying capacity is reduced by some natural or human phenomenon.
The assertion that the environment is being degraded or that a species is a "weed" contains an hypothesis that can be tested, if carefully stated and studied in a relevant context.
Example: Environmental Protection Agency - Biological Criteria for Coral Reef Ecosystem Assessment
• presence of human fecal waste/pollution (commonly assessed by nitrogen isotope ratios in tissues of reef organisms)
• dying native species (change of community structure, especially for the soft bottom dwellers)
• invading species - weeds in the broad sense of intrusion, replacement of native species (change of community structure)
Weeds as Agents of Environmental Degradation
Weeds are subject to the administrative influences on their definitions, as we discussed above. The Australian government provides us with a "top down' definition of weediness.
• invasiveness and impacts
• potential for spread
• socioeconomic and environmental values
• effects on biodiversity
The counties in the US states of Montana and Washington provide us with "bottom up" views of weed characteristics.
• Montana - Yellowstone County : Noxious weeds are non-native plants that have become established or that may be introduced in the state. These NOXIOUS WEEDS may render land unfit for agriculture, forestry, livestock, wildlife or other beneficial uses.
• Washington - Whatcom County
Class A Weeds: not native to state, limited distribution, new invader, serious threat, prevention of seed production mandated, goal of eradication
Class B Weeds: not native to state, abundant or widespread, control at county discretion
Class C Weeds: any other noxious weeds, abundant in some areas, serious threat to uninfested areas, prevention of seed production mandated in selected areas, goal of containment with eventual eradication
Control of invasive species requires regional cooperation because administrative units like states are not ecological units like air sheds or watersheds.
Example of Weeds from the Butler County, Ohio, GARDEN OF WEEDY DELIGHTS
- large and small foxtail species (Asian origin and a weak competitor with other weeds after it moves into bare disturbed sites)
- small clover (note nodules on roots that contain N-fixing bacteria)
- oxalis (similar in appearance to clover but spreads not only by seeds by subterranean shoots)
- spiny cucumber vine (annual native, spreads by seeds)
- vine milkweed (perennial, spreads by wind-borne seeds and by subterranean shoots)
- acalypha/copperleaf - rampant reproduction by seeds, annual
- Jerusalem Artichoke - native sunflower spreads mainly by subterranean shoots: seed production minimal (tops make good livestock fodder, parts of underground stems edible and used by local native Americans as food in times of drought)
Concluding Thoughts
Notice that the weedy examples do not clearly fit administrative definitions and/or can escape control because the emphasis on control is through blocking seed production. There are also many weeds that cannot be eradicated by mowing or cultivation (fragments subterranean shoots and replants them). Some weeds are actually spread by mowing because their seeds stick to undersides of mower decks and transfer to the next site.
Studying weeds brings us to an understanding of their biology as well as with the interdisciplinary activities of their definition and management. This requires that scientists communicate how they think about problems, that social scientists/political office holders communicate with scientists and both need to ask for input from the humanities (values, aesthetic issues, philosophical perspectives).
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Links, Sources
My garden and lawn.
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