WHAT [AND WHERE] IS BIODIVERSITY?

NRE 220 Lecture 1

Corresponding Readings in Primack, Richard B. Essentials of Conservation Biology.
Chapter 3: pages 55-76

Introduction

Humankind depends on solar energy and the natural resources of the earth for food, shelter, clothing and medicines. Many natural resources are renewable, and require careful management in order that we may use them forever. The biological resources available to us are a consequence of the earth's biological diversity.

What is biological diversity? Biological diversity refers to the number and variety of species, ecological systems, and the genetic variability they contain. It often is used more narrowly to refer to the number of species on the planet.

Humankind entered the modern industrial age with biological diversity at a historic high. Yet, as future lectures will describe, we are in a period of increased extinction rates, and this trend is now accelerating rapidly. This is taking place despite some very good conservation efforts over the past century, including the creation of numerous parks and the establishment of conservation policies in many countries. This course addresses why this extinction wave is taking place, and what can be done about it. Today we ask, what is biodiversity, and what do we know of this subject?

How Many Species Exist Today?

"known" species are those that have been named and formally classified

1.4 million named species include ~ 750,000 insects, ~250,000 flowering plants

actual number of species is estimated at 10-30 million, based on ratios of unknown to

known species in studies by specialists

some groups (birds, mammals, flowering plants) are mostly "known"; other groups

(insects, microbes, freshwater fishes) are largely or mostly "unknown"

The Geographic Distribution of Biodiversity

Latitudinal diversity gradients: more species are found in the tropics than in temperate regions, which in turn are more diverse than polar regions. Possible explanations include: (1) high productivity of tropics, (2) more intense species interactions, (3) greater environmental stability, and (4) greater environmental constancy.

Hotspots: more species are found in some areas for non-obvious reasons, perhaps having to do with favorable circumstances for species formation.

Endemism: Endemics are species that are unique to an area, presumably because they evolved there. Tropical locales and remote islands often have many endemic species.

 

The Geographic Distribution of Biomes

The distribution of major ecosystem types is determined by climate. When a large area of earth is covered by a particular ecosystem that can be characterized by the dominant vegetation type, this is called a biome. The humid tropical forests are found near the equator, where it is both warm and wet, and in their original extent covered ~ 15% of the land surface of earth.

TRANSPARENCIES: 1. Some key issues in global change, 2. Biodiversity -- giant beetle, tiny elephant, 3. Biodiversity – pie chart, 4. Biodiversity – Far Side cartoon, 5. Biodiversity – definition, table of numbers of species, 6. The Geographical Distribution of Biological Diversity, 7. Latitudinal Gradients: Number of mammal species in tropical and temperate countries, 8. Potential explanations of latitudinal diversity gradients, 9. Hot spots, 10. Endemic species: Numbers in some hotspot areas, 10. World Biomes

LINKS:

• Biodiversity: Measuring the Variety of Nature: Learn about how biodiversity is measured and areas that need to be conserved.
• Ecology, Biodiversity, and Environment: Browse this "Virutal Library" site from Rice University with a good database on endangered extinct species, and much more!
• Conservation International: This sites offers information on megadiversity and global hotspots that need to be protected for biodiversity.
• The Biodiversity Center: Biodiversity basics presented by the Defenders of Wildlife.

RELATED ARTICLE(S):

• Diversity by Default by David Tilman