Controls: humans Self-scouring, steel-bladed plow <0.01% of pre-settlement prairie in Illinois remains
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
Variation in temperature generates winds. Winds drive ocean currents, which redistribute heat and moisture. clockwise counter- clockwise upwelling
Upwelling currents bring cold, nutrient-rich water to the surface & lead to high productivity
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