Non-Native Species - Delaware Water Gap National Recreation Area (U.S. National Park Service) Autumn olive (dark bluish-green) invades a former crop field. NPS Photo by Bill Agne. Invasive exotics are not only plants, some of them are insects as well. Hemlock woolly adelgid is an aphid that attacks and kills hemlock trees-- trees that can normally live up to 400 years. Hemlock trees are a key component of our forested ecosystem, important for fish, birds, mammals and insects alike. Human populations within a 6-hour drive of the Water Gap are expected to double within the next 20 years from 60 million to 120 million. With all of the construction, disturbance to natural systems, and land use requirements it will entail to house these people, native plant populations and ecosystems will be further stressed and even now-common native species may be in danger of decline. It will be more important than ever for protected areas such as national parks to serve as reservoirs for native species.
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