A sea of invasive torpedo grass (Panicum repens), up to 1 meter deep, stretches to the horizon on West Ship Island of the Gulf Islands National Seashore, Mississippi, in the United States. Invasive common reed (Phragmites australis) at right. Image Credit: Hans Landel

The human-assisted movement of species from one place to another in the world is an ancient phenomenon. Now, our ability to travel more widely and quickly has increased the number and ability of species to be dispersed into new habitats.

Sometimes, these non-native species find their new homes most amenable and they increase in population size. In the process, they cause ecological damage, and possibly negatively impact local economies and human health. When they do, they have become members of that class of pests we call ‰invasive species.‰ During this quarter, IEEE Earthzine will address the challenges and issues posed by invasive species, and some of the solutions being employed.

In 1999, then-U.S. President Bill Clinton issued Executive Order 13112, in which an invasive species is defined as ‰a species that is non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.‰Û

The negative impact of invasive species on the world’s biodiversity is second only to habitat loss; a major component of their impact is their effects on habitat. They can outcompete, prey upon, cause diseases in, hybridize with, and even cause the extinction of native species. They can change the ecological interactions, the hydrology, the fire regimes, and nutrient cycling within an ecosystem.

Invasive species also impact humans through economic and health damages. For example, a 2011 study concluded that more than $3.8 billion per year in total costs and losses occur in the United States due to non-native forest insects alone.

Invasive species are a distinctly human-caused problem. We move them, introduce them and cultivate them—sometimes intentionally, sometimes not. As such, we have the responsibility of dealing with them.

First, their spread must be stopped or minimized. Second, once they have invaded, they must be controlled, managed, and/or eradicated/eliminated. Third, it is paramount that the public learn about invasives and the problems they cause, and become involved in their control. Fourth, policies, regulations, and legislation must be enacted to address invasive species, including the funding of programs and research. Finally, research is required to increase our understanding of several topics:

• • their biology, in their native and adopted environments

• • the effects of climate change

• • how we move them around (how they spread)

• • their impacts on native species and landscapes, negative and positive

• • their impacts on human health

• • their impacts on the economy

• • how to increase public awareness (and thus support of control efforts)

• • how to detect and monitor them

• • how to evaluate the invasive potential of non-natives

• • how to promote policy/legislation

• the efficacy of various detection and control methods.

There are many methods for meeting the challenge of invasive species. Control measures include chemical; physical, such as pulling invasive plants and cutting infested trees; cultural, such as burning, mowing or using mulch; and biological, such as using biocontrol agents or genetic engineering.

Technical advances are continually being developed to improve the way we manage invasives. For example, managers are using herbicide-filled paintballs to target hard-to-reach invasive plants on cliff faces from helicopters, dogs to detect wood-boring beetle larvae hidden in wood or zebra mussels attached to boats (and even water containing their microscopic larvae), remote sensing to study changes in vegetation, and environmental DNA to detect the presence of invasive aquatic organisms. Citizen science programs play an important role in detecting, mapping and controlling invasives. These and many other programs and campaigns work to engage the public and increase awareness. Finally, governments at various levels have been enacting legislation and policies to address invasive species.

We also must consider the philosophical questions posed by invasive species: When should an introduced species be considered native, if ever? When do we give up trying to control an invasive species, if ever? How do we prioritize which species to manage, and when and where (a common question in conservation)? Are invasives ever a benefit?

Over the course of the coming quarter, we will bring you articles that cover many of these topics and issues. Our intent is to inform, motivate and inspire our readers, and in the process provide hope for the future. We are confident that you will return often to see what new articles are awaiting you.

Hans Landel, Ph.D., is the guest editor of IEEE Earthzine’s invasive species theme, Ecological Impacts of Biological Invasion. Dr. Landel also is the Invasive Species Program coordinator at the University of Texas Lady Bird Johnson Wildflower Center in Austin, Texas.