Understanding the Different Ecosystems of the United States
Published December 15, 2025 · American Nature Journal Editorial Team
An ecosystem is the set of living things in a place together with the physical conditions they depend on. A few variables explain much of the variety across the country.
Temperature and precipitation
Where rainfall is abundant, forests usually dominate. As precipitation decreases, grasslands replace forest, and with even less water, desert vegetation takes over.
Elevation
Climbing a mountain produces changes similar to travelling far north: forest gives way to stunted trees and finally to alpine tundra above the tree line.
Water and soil
Wetlands, rivers and lakes create their own conditions regardless of the surrounding climate, and soil type strongly influences which plants can grow.
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