Non-native species and pathogens have caused enormous ecological and economic damage to U.S. forests and grasslands, and they continue to be introduced at an alarming rate. Non-native species have been imported intentionally and unintentionally through world trade and foreign travel, and they have been able to adapt to new environments and spread rapidly. Their success is often due to a lack of both host resistance and natural enemies, allowing them to establish in new environments unimpeded. This has cascading impacts on other species.

Understanding and managing invasive species is critical for protecting and restoring resilient forest and grassland ecosystems. Forest Service research on invasive and exotic species directly advances efforts to rapidly discover and respond to emerging threats. This includes informing government regulations to limit the accidental importation of pests and pathogens, detecting threats as early as possible, and eradicating invasive pests and pathogens when feasible.

The Forest Service invests in research on invasive and exotic species because:

• There are more than 450 known forest insect and pathogen species established in the continental U.S.

• Approximately 2.5 established non-native forest insects were detected in the U.S. each year between 1860 and 2006.

• At least 18 percent of introduced insects and all 16 introduced pathogens have caused tree damage that impacts forest health and productivity and sometimes causes extensive tree mortality. For example, the emerald ash borer is the most damaging invasive forest insect pest in North America, having killed hundreds of millions of ash trees across the U.S. since it was introduced. Forest Service researchers study risk, effects, detection, spread, biology, ecology, control, and management of emerald ash borer as well as other invasive forest insects including gypsy moth, hemlock woolly adelgid, and spotted lanternfly.

• Mortality caused by non-native invasive forest pests impacts carbon dynamics by reducing forests’ carbon sequestration capacity and converting live materials that previously stored carbon to dead carbon sources.

Featured Work

• Invasive Species in Forests and Rangelands of the United States: A Comprehensive Science Synthesis for the United States Forest Sector describes the serious threat of invasive species to native ecosystems.  It covers species of all taxonomic groups from insects and pathogens, to plants, vertebrates, and aquatic organisms that impact a diversity of habitats in forests, rangelands and grasslands of the U.S.

• Non-Native Genetic Sampling Research from the National Genomics Center for Wildlife and Fish Conservation uses forensic-style DNA samples, such as hair, scats and feathers collected without ever seeing an animal, to monitor rare and sensitive species. 

• A field guide for the identification of invasive plants in southern forests provides information on accurate identification of the 56 nonnative plants and groups that are currently invading the forests of the 13 Southern States.