PATTERNS OF LIFE: Biogeography

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Chapter Outline

7.1

Biogeographic Patterns
7.2

Setting the Boundaries: Limiting Factors
7.3

Moving Around: Dispersal
7.4

Starting Anew: Ecological Disturbance and Succession
7.5

Three Ways to Organize the Biosphere
7.6

Geographic Perspectives: Journey of the Coconut

The Avenue of the Baobabs, near the town of Morondava in Madagascar. Baobab trees (Adansonia grandidieri) are often called ‘upside-down’ trees because their branches look like roots.

(© Philippe Michel/age fotostock)

LIVING PHYSICAL GEOGRAPHY

Why do animals migrate?
Why do cacti have spines?
How are wolves important to ecosystems?
Why do coconuts float?

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THE BIG PICTURE

Geographic patterns of life are determined by natural factors and by human activities. The biosphere can be organized by flows of energy and matter, by genetic similarities among organisms, and by ecological units of life.

LEARNING GOALS

After reading this chapter, you will be able to:

7.1

Identify and explain major geographic patterns of life on Earth.
7.2

Discuss factors that limit the geographic ranges of organisms.
7.3

Explain how organisms expand their geographic ranges.
7.4

Discuss the role of ecological disturbance and the return of life following disturbance.
7.5

Describe three approaches to organizing the biosphere.
7.6

Assess the relationship between people and the coconut palm and apply that knowledge to other organisms used by people.

THE HUMAN SPHERE:

Exotic Invaders

NON-NATIVE (or exotic) organisms are those that have been moved outside their original geographic range by people. Some non-native organisms cause ecological damage by preying on or taking resources in their new ranges from native organisms (those that were there originally). In many areas where non-natives are successful, their natural predators are missing. For example, the Nile perch (Lates niloticus) (Figure 7.1), which was intentionally brought into Lake Victoria in eastern Africa in the 1950s as a food resource for local communities, has had significant negative effects on native fish species in the lake.

Figure 7.1

A Nile perch. The non-native Nile perch has inflicted serious ecological damage in Lake Victoria. It preys on the lake’s native cichlid fish and has driven about 300 cichlid species to extinction or near-extinction. Nile perch grow to nearly 2 m (6.5 ft) and can weigh 200 kg (440 lb).

non-native

(or exotic) An organism that has been brought outside its original geographic range by people.

Today, non-native species are implicated in extinctions worldwide. About 50,000 non-native species have been introduced into the United States (although not all of them are harmful). Among the U.S. states, Hawai‘i has a particularly serious problem with non-native organisms. Hawai‘i has no native reptiles (such as snakes and lizards), no native amphibians (such as frogs), no native parrots, no native ants, and only one native mammal—a bat. Today, Hawai‘i has many non-native organisms introduced by people, including escaped garden plants, wild pigs, piranhas, game, bass, trout, chickens, rats, mongooses, cats, snails, frogs, insects, cattle, deer, boa constrictors, and goats, among others. Many of these non-natives are threatening the islands’ native organisms. Hawai‘i incurs about a half billion dollars a year in crop losses, property damage (from non-native termites and rooting wild pigs), and costs to fight the invaders.

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However, some non-native organisms are vital to the economy. Hawaiian crops such as cattle, sugarcane, pineapple, and banana are not native to the islands. Without these non-native organisms, the Hawaiian economy would be relatively limited.

This chapter highlights major geographic patterns of life on Earth and focuses on the processes that shaped these patterns. It explores the movements of organisms across Earth’s surface and the roles of fire and other forms of ecological disturbance. It also develops three approaches that allow us to categorize and organize the biosphere. Finally, the Geographic Perspectives at the end of the chapter examines the history of the coconut palm through the eye of a geographer.