BIO330H5 Lecture Notes - Primary Producers, Primary Production, Ecosystem Services
This preview shows half of the first page. to view the full 1 pages of the document.
Chapter 56: Ecosystem and Global Ecology
56.2 How Does Energy Flow Through the Global Ecosystem?
Solar energy drives ecosystem processes
Solar energy enters ecosystems by way of plants and other photosynthetic organisms.
Only about 5 percent of the solar energy that arrives on Earth is captured by photosynthesis;
remaining energy is either radiated back into the atmosphere as heat or taken up by the
evaporation of water.
Gross primary productivity (GDP) is the rate at which energy is incorporated into the bodies of
The accumulated energy is called gross primary production.
Primary producer use some of this accumulated energy for their own metabolism; the rest is
stored in their bodies or used for their growth and reproduction.
The energy available to organisms that eat primary producer, called net primary production
(NPP), is gross primary production minus the energy expended by the primary producers during
Only the energy of an organism’s net production is available to other organisms that consume it.
The geographic distribution of the energy assimilated by primary producers reflects the
distribution of land masses, temperature, and moisture on Earth.
Production in aquatic ecosystems in limited by light, which decreases rapidly with depth; by
nutrients, which sink and must be replaced by upwelling of water; and by temperature.
Human activities modify flows of energy
Some human activities decrease net global primary productivity (e.g. conversion of forests).
56.4 What Services Do Ecosystem Provide?
Ecosystems provide people with a variety of goods and services.
The rapidly expanding human population has greatly modified Earth’s ecosystems to increase
their ability to provide some of the goods and services it needs, particularly food, fresh water,
timber, fiber, and fuel.
The most important driver of alterations in ecosystems and the services they provide has been
changes in land use as natural ecosystem have been converted to other, more intensive uses.
The modifications of ecosystems to benefit human beings in one way has often resulted in the
degradation of other services.
56.5 What Options Exist to Manage Ecosystems Sustainably?
Often the total economic value of a sustainably managed ecosystem is higher than that of an
intensively exploited ecosystem (e.g. land for clear cutting).
A major barrier to achieving these greater long-term benefits is that many ecosystem services
are considered “public goods” that have no market value.
More sustainable use of fresh water can be achieved by charging the full cost of providing the
water, by developing methods to use water more efficiently in agriculture and by altering the
allocation of water rights so that the incentives favour conservation.
Sustainable use of marine fisheries can be achieved by establishing more marine protected
reserves and flexible no-take zones where fish can readily grow to reproductive age; establishing
and implementing a limit to the number of fishing permits can increase the total economic value
of the fishery and provide better fish to consumers.
You're Reading a Preview
Unlock to view full version