To conserve and manage our biological resources wisely, we must understand the basic concepts of energy, energy flow in ecosystems, and biological production.  This section should foster your understanding of material covered in the text about biological production and sustainable use of forests and other biological resources.

CASE STUDY - Harvesting of Forests in Michigan and England. 

   Today there is much concern with the sustainability of the planet's biological resources, including forests, wildlife, and fish.  We seem to be in the process of destroying many of these resources by harvesting them faster than they can regrow, and we have been doing so for a long time.   For example, in the United States, between 1840 and 1920, 19 million acres of white pine forests were logged in the state of Michigan alone.  Only 49 acres of uncut white pine remain in Michigan, and only a small fraction of the original white pine forestes have regenerated to anything like their original size and abundance.  As a result of these practices, stump barrens, areas where large trees have never regrown due to fires that destroyed the organic matter in the soil, are common in northern Michigan.

   In contrast, in medieval England, some small forested areas were harvested carefully and slowly.  For example, in 1356, a survey of the estates of Bishop Ely stated that a "certain wood called Heylewode" was 32.4 ha (80 acres) in size.  Every year the "underwood" (the shrubs and young, small trees) was harvested in 4.5 of the 32.4 ha (11 of the 80 acres), leaving mature trees everywhere and young trees on the remaining 27.9 ha (69 acres).  This practice was continued "without causing waste or destruction;" in modern terminology, the practice was sustainable.  Today, we are seeing projects designed to redevelop these methods.

   These two contrasting examples suggest that at certain levels of harvesting forest production can be sustained, but once these levels are exceeded, forests will decline and may not recover.  Throughout the history of civilization, people have cut trees faster than trees have regrown.  The management of forest resources involves various aspects of environmental science such as analyses of carrying capacity and other areas of biological conservation.