Controls: climate
Controls: soils, parent material
Controls: topography
Controls: disturbance
Controls: humans
Self-scouring, steel-bladed plow
<0.01% of pre-settlement prairie in
Illinois remains
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
Variation in temperature generates winds.
Winds drive ocean currents, which redistribute heat and
moisture.
clockwise
counterclockwise
upwelling
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
• Shifts in distributions
(1-3)
• Community
disaggregation (1 & 3)
• New communities (2
& 3)
• Extinction (4)
Williams et al. 2007. PNAS.
Maps of novel 21st-century climates and
disappearing 20th-century climates
12-39%
4-20%
10-48%
4-20%
Assumes no dispersal limitation; w/ disperal limitation the %s approx. double
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