Conservation Biology- Lecture 2 GLOBAL PATTERNS AND PROCESSES

GLOBAL BIODIVERSITY

The world comprises an enormous variety of habitats and ecosystems

The number of which and their topographic complexity is one measure of the ecological diversity in a region

In general the world is divided into a number of ‘biomes’ – defined by their dominant vegetation type

Plants, in general, are the keystone group of organism used to classify terrestrial ecosystems 

FACTORS WHICH INFLUENCE VEGETATION

Climate

• temperature
• precipitation
• seasonal variation (low in tropics)

Soil

• texture (clay vs. sand)
• structure (aggregation of types)
• permeability

Most ecosystem descriptions try to combine an assessment of habitat (plants/soil) and climate

For example, ‘tropical rain forest’ or ‘dry savannah bushland

Species diversity patterns and mechanisms implicated in its regulation

The earth is not uniform in temperature and species diversity reflects this non-uniformity

General patterns have been studied and known for many years (e.g., most diversity resides in the tropics)

However explaining these patterns is not always simple and often several/many mechanisms and processes are implicated:

•  ecological
• evolutionary
• geological/geomorphological
• biogeochemical
• biogeographical

Simple trends: rainfall increases with temperature…

 Simple trends: species diversity increases nearer the equator…

Other recognised patterns

Altitude gradients: Species richness declines with altitude

Primary productivity: Correlates with species diversity

Area : Species/area relationship

Habitat age: Species diversity accumulates with time

Many exceptions.. e.g. tropical rainforest (7% of earth's land mass, 50% min. of known species).

Biogeography: Space + Time = Biodiversity? ­

• Studying patterns of current diversity has received much attention in the last 20 years (pattern) ­
• But it is equally important to understand what happened in the past (process) ­
• Without understanding processes, how can we predict the future? 

Biogeography and the first explorers…

• Charles Lyell (geologist: “Principles of geology”)
• Alfred Russell Wallace (the father of ‘zoogeography’)
• Charles Darwin (“The Origin of Species”)
• Banks/****** (botanical biogeography)

Darwin and Wallace’s observations on…