Page 701 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 20 Terrestrial Biomes 665
Sanctuary within the California Current LME and the Florida Keys Marine Sanctuary within the Gulf of Mexico LME (see sanctuaries.NOAA.gov/).
Anthropogenic Biomes
Even in many of the most pristine ecosystems on Earth, evidence of early human settlement exists. Today, we are the most powerful biotic agent on Earth, influenc- ing all ecosystems on a planetary scale (Figure 20.23). Scientists are measuring ecosystem properties and building elaborate computer models to simulate the evolving human—environment experiment on our planet—in particular, the shifting patterns of environ- mental factors (temperatures and changing frost peri- ods; precipitation timing and amounts; air, water, and soil chemistry; and nutrient redistribution) wrought by human activities.
In 2008, two geographers presented the concept of “anthropogenic biomes,” based on today’s human-altered ecosystems, as an updated and more accurate portrayal of the terrestrial biosphere than the “pristine” natural
vegetation communities described in most biome clas- sifications. Their map, shown in The Human Denomina- tor 20, shows five broad categories of human-modified landscapes: settlements, croplands, rangelands, forested lands, and wildlands. Within these categories, the sci- entists defined 21 biomes, which summarize the current mosaic of landscapes in terms of common combinations of land uses and land cover.
Anthropogenic biomes result from ongoing human interaction with ecosystems, linked to land-use prac- tices such as agriculture, forestry, and urbanisation. The most extensive anthropogenic biome is rangelands, coveringabout32%ofEarth’sice-freeland;croplands, forested lands, and wildlands each cover about 20%, and settlements take up about 7%.
The concept of anthropogenic biomes does not replace terrestrial biome classifications, but instead presents another perspective. Understanding of the natural biomes presented in this chapter is essential for the advancement of basic and applied sciences as they relate to conservation biogeography and ecosys- tem and species restoration.
▲Figure 20.23 Freeway through the Puerto Rican rain forest. Humans are Earth’s most powerful agent of geomorphic and biotic change. The human denominator influences all biomes and all Earth systems. [Bobbé Christopherson.]