Human populations have become highly mobile over the past two centuries. Innovations in transportation, such as airplanes and cargo ships, have facilitated the movement of both people and the goods they consume. Grocery store shelves are brimming with imported goods, from Chilean raspberries to bananas from Madagascar. Lush rainforest plants fill nurseries and tropical hardwoods are sold at lumberyards. Globalization has opened up a world of commerce possibilities, but the movement of foreign goods comes with an often unaccounted for risk- the introduction of invasive species.

Most of the foreign plants and animals that enter our country's borders each year are benign, temporarily filling our gardens or plates. But some, due to aggressive traits, favorable environmental conditions, and/or a lack of predators, become a serious problem. Dubbed invasive species, these non-native organisms have the ability to cause serious economic or environmental harm.

Often, they are unintentional imports; Asian long-horn beetles were living in wood used to make packing pallets, zebra mussels were accidentally transported in ship ballast water discharge. Others were intentionally introduced to provide certain functions— kudzu was used to prevent soil erosion, settlers planted garlic mustard for an early-season potherb— before realizing how aggressive these species could be once established.

Institute ecologists are at the forefront of invasive species research. From unraveling the impact that zebra mussels have in the Hudson River to predicting how forests will change as a result of beech-bark disease— by understanding how invasive species impact ecosystems, Institute research helps inform management decisions.

A sampling of research includes:

	A floating-leaved aquatic plant introduced into New York during the 1800's, water chestnut is now abundant in the Hudson River. Dr. Nina F. Caraco, with colleagues, has shown that the plant causes a reduction in an essential aquatic resource— dissolved oxygen. Current research is exploring the impact plant beds have on nutrient cycling and green house gasses, as well as impacts on invertebrates and fish.
	Introduced in ship ballast water during the 1980's, zebra mussels are a nuisance in the Hudson River. Their filtering activity reduces the abundance of both animal and plant life in the water column (phytoplankton and zoolplankton), and their spread has been linked to native mussel loss and fish population changes. A team of Institute scientists, including Drs. David L. Strayer, Nina F. Caraco, Jonathan J. Cole, Stuart E. G. Findlay, and Michael L. Pace, is investigating the impact these invasive bivalves have on the Hudson River ecosystem.
	Beech bark disease and the gypsy moth are both examples of invasive species that have altered forest composition on invaded sites. Drs. Gary M. Lovett and Kathleen C. Weathers are researching the changes these exotics cause in forest nitrogen cycling, decomposition rates, and soil acidity.
	The competitive success of some invasive species is linked to their ecosystem effects. Altered habitats benefit the invader, while making the site less hospitable to native inhabitants. Understanding the legacy invasive species leave behind is critical for successful restoration of plant communities and ecosystem function. When restoring native plant communities, invasive species and their soil legacy may need to be removed.
	In most forest soils, the deep litter layer provides critical habitat for forest floor species. This layer exerts strong controls on nutrient cycling, nutrient retention, and seed germination. Exotic in the northeastern U.S., earthworms can transform the forest floor, impacting all of these processes. Microbial biologist Dr. Peter M. Groffman is researching the impact that earthworms have on forest soils.
	Drs. Steward T. A. Pickett and Mary L. Cadenasso are investigating the relationship between diversity and exotic plants, with the goal of understanding how invasive plants establish in urban and rural ecosystems.