Page 700 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

664 part IV Soils, Ecosystems, and Biomes
(a) On St. Helena, endangered native species grow in greenhouses and will be eventually planted in the wild.
(b) Endemic species across the island were severely depleted during the age of exploration; shown here is Jamestown, the capital city on the northwest shore.
▲Figure 20.22 Ecological restoration on Saint Helena island, located at 16° S latitude in the Atlantic Ocean. [(a) robert Christopherson. (b) Bobbé Christopherson.]
of landscape-scale think- ing for species preserva- tion. Although present research goes beyond the original theory, the basic conceptual ideas inform conservation science, es- pecially with regard to proper formation of parks and reserves.
Aquatic Ecosystem
Management
Human activities have affected aquatic ecosys- tems, whether freshwa- ter or marine, in roughly similar ways to terrestrial ecosystems. Coastal ocean
on an island to the island’s size and distance from the mainland.
The theory summarized three patterns of spe- cies distributions on islands: (1) The number of species increases with island area, (2) the number of species decreases with island isolation (dis- tance from the mainland), and (3) the number of species on an island represents an equilibrium between the rates of immigration and extinc- tion. Larger islands have a wider variety of habi- tat and niches, and thus lower extinction rates. This theory provided the foundation for under- standing “islands” of fragmented habitat, inspired thousands of studies in biogeography and ecol- ogy, and increased awareness of the importance
The principles developed in the study of isolated species’ evolution and decline with the introduction of non-native species on islands have become useful con- cepts informing global conservation efforts. One strategy for conservation of species is to focus on habitat preserva- tion, such as setting aside parks and wildlife refuges. Yet these protected areas are often isolated, surrounded by human development and disconnected from other natu- ral habitat. Such habitat fragmentation is problematic for species requiring a large range for survival. In the 1980s, researchers discovered that a number of U.S. national parks had become isolated “islands” of biodiversity and some species within them were declining or disappear- ing completely.
A key conceptual model for understanding the ef- fects of habitat fragmentation was Robert MacArthur and E. O. Wilson’s theory of island biogeography, pub- lished as a book by the same name in 1967. The theory, based on scientific work on small, isolated mangrove is- lands in the Florida Keys, links the number of species
waters, in particular, continue to deteriorate from pol- lution and habitat degradation, as well as unsustainable fishing practices. Declines in aquatic species, such as the precipitous drop of the herring population in the Georges Bank fishing area of the Atlantic in the 1970s, highlight the need for an ecosystem approach to under- standing and managing these international waters.
This need was partly met by the designation of large marine ecosystems (LMEs), distinctive oceanic regions identified on the basis of organisms, ocean- floor topography, currents, areas of nutrient-rich upwelling circulation, or areas of significant preda- tion, including human. Examples of identified LMEs include the Gulf of Alaska, Hudson Bay, Newfoundland and Labrador Shelf, Northeast Continental Shelf, and Baltic and Mediterranean Seas. Some 64 LMEs, each encompassing more than 200000 km2, are presently defined worldwide (see the list at www.lme.noaa.gov/). A number of these LMEs include government-protected areas, such as the Monterey Bay National Marine