Controls: climate

Controls: soils, parent material

Controls: topography

Controls: disturbance

<0.01% of pre-settlement prairie in Illinois remains

Self-scouring, steel-bladed plow

Controls: humans

Controls: herbivory

Controls: microclimate

Controls are not constant; they have changed through time

For example:

• Continental drift• Mountain building and rain shadows• Climate change• Human alteration to land cover; greenhouse gas

emissions

Biomes during last glacial maximum

Trees following last glacial maximum

Latitudinal movement of the solar equator causes seasons

Solar equator moves seasonally

Seasonal cycles in temperate lakes

clockwise

counter-clockwise

upwelling

Variation in temperature generates winds.

Winds drive ocean currents, which redistribute heat and moisture.

Upwelling currents bring cold, nutrient-rich water to the surface & lead to high productivity

Effects of El Niño on climate

Effects of El Niño on crop production

Stronger El Niño events in recent decades

Fundamental niches and climatic envelopes for hypothetical 20th- and 21st-century climates

Williams et al. 2007. PNAS.

• Shifts in distributions (1-3)

• Communitydisaggregation (1 & 3)

• New communities (2 & 3)

• Extinction (4)

Maps of novel 21st-century climates and disappearing 20th-century climates

Assumes no dispersal limitation; w/ disperal limitation the %s approx. double

12-39%

10-48%

4-20%

4-20%

Williams et al. 2007. PNAS.

Summary

• Ecosystems are complex, resulting from many interacting factors

• Ecosystems and their controls are not constant; they have changed through time

• Humans now have a dominant influence on Earth’s climate and ecosystems

• The present helps us interpret the past and anticipate future changes