Urban Regions : Ecology and Planning Beyond the City

Ecosystem, community, and population ecology 83

Figure 4.1Akeystone top predator, Florida panther (Puma concolor coryi). A globally

threatened subspecies with fewer than 100 animals believed to exist; endemic to

South Florida. Hollingsworth photo courtesy of US Fish and Wildlife Service.

Using light energy and chlorophyll, green plants photosynthesize, which
effectively absorbs carbon dioxide and water to make carbohydrate and give off
some oxygen. Thus plant cover, from green roofs to coastal marshes and farm-
land, helps somewhat in reducing greenhouse gases by absorbing CO 2 ,though
forests and woodlands have the added advantage of holding the carbon for
decades. The carbohydrate made by plants is the basis of biomass and these food
chains.
Although much variation exists, the food chain may have anenergy efficiency
of about 10 %. Each time biomass energy changes in form much heat is given
off (as described by the second law of thermodynamics), and in this case about
90 % of the biomass energy in one level never makes it to the next level. The