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Invasions and extinctions are occurring at a rate that is unprecedented in historical time. These phenomena are a kind of biological extreme at each end of the spectrum, and both are responses related to landscape and environmental conditions, which also link to climate change. Research shows that species change their ranges in response to climate change and to general predictable trends, but individual responses seem to be idiosyncratic, said moderator Craig Allen. Because of this, there is a need to explicitly anticipate and think about ecological surprises and the unanticipated consequences of global change. Ecological systems often exhibit nonlinear threshold responses, so systems can change suddenly in response to a slow force such as climate change.
The Platte River Basin can provide a focal point for the study of invasion and extinction and other effects on species related to changes in climate. The Platte River provides critical habitat for many species, including four threatened and endangered wildlife species: the least tern, piping plover, whooping crane and pallid sturgeon. The shallow riverine wetlands along a narrow 100-mile stretch of the central Platte River provide a crucial stop-over for whooping cranes and more than 500,000 sandhill cranes each spring during their northward migration. Approximately 300,000 shorebirds comprising more than 30 species migrate through the North American Migratory Flyway that transects Nebraska. At the other biological extreme, low water levels in the Platte induced by drought have led to invasive species problems. For example, the common reed Phragmites australis is choking the river channels and hindering habitat restoration efforts.