For instance, many of the trees they planted to create a rain-forest ecosystem grew rapidly but then fell over before reaching maturity. The designers had not realized that young trees need wind to grow properly. When the wind blows, it bends the tree, which tugs at the roots on the windward side and compresses the wood on the other side. In response, the root system expands to provide a firmer anchor where it is needed, and the compressed wood cells change their structure to become stronger and firmer.
