An environmental change can produce effects beyond the place where it begins. Local deci sometimes al distant condi because flo water a moving ani carry mate across bound that peo establish bet neighboring regions. A boundary drawn on a map may be useful for administration without stopping a physical process. For this reason, communities sharing a river often need to exchange information about conditions upstream and downstream. Understanding the connections can reveal why an apparently local problem requires cooperation. The relevant area is defined partly by how the process operates.

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