May 6, 1999

Testimony of Peter M. Rice

Senate Agriculture Committee

Hearing on Noxious Weeds

May 8, 1999

Nampa, Idaho

Peter M. Rice

Division of Biological Sciences

University of Montana

Missoula MT 59812

biopmr@selway.umt.edu

406-243-2671

http://invader.dbs.umt.edu

The Magnitude of the Weed Invasion

The exotic plant invasion phenomenon consists of thousands of exotics being continuously introduced to North America from portions of other continents that have similar climatic conditions. A summary analysis of INVADERS Database System indicates that as of 1997 at least 996 alien plants have been reported as established in agricultural and wildland settings in the five northwest states WA, OR, ID, MT, WY (Rice 1999).

A detailed examination of verifiable distribution records in INVADERS shows that prior to 1907, during a period of little regulation of the importation of goods and agricultural commerce, about one hundred exotics per decade were establishing in the five northwest states. During the period of World War I , the Great Depression, and World War II, the number of successful introductions declined to about 40 species per decade (see two figures on page 3). With the expansion of global travel and commerce since the 1960's the number of new introductions is again approaching the pre-twentieth century rate despite the enactment of numerous regulatory mechanisms.

After initial colonization, often at several locations, these species take several decades to a century or longer to expand to their maximum geographic range. The spatial scales can be a portion of a single state to multi-state regions, and almost all of North America for the weeds with the broadest ecological amplitude. The Flora of North America project estimates that there are 3,766 exotics among the 22,008 species that exist outside of horticultural settings in North America. (Kartesz 1999, personal communication). At least 1,100 of these exotics are believed to be problematic invasive weeds.

Most exotic weeds established in North America over the past century originated from southern Europe, the Mediterranean Basin, and southwest most portions of Asia. The early invaders came from this region because many weeds co-evolved with the development of agriculture and livestock grazing, historic trade and emigration, and climatic similarity to much of the United States. Since 1950, 71% of the new invaders have also came from this historic emigration and trade region of Eurasia. However the other 29% of alien weeds invading since 1950 have come from eastern Asia, Africa and South America (Toney, Rice and Forcella 1998). As the global economy, trade and travel continue to expand in the next century we can expect to see a new wave of introductions from climatically analogous regions which include northern China, the South African grasslands, and the pampas of South America (see Mack 1996, Rejmanek 1996, Reichard and Hamilton 1997, others).

Lines of Defense

Forcella and Harvey (1983) used county presence / absence data to analyze the number of exotic weed species and their relative abundance in the Pacific Northwest region from 1900 to 1980. They concluded that the steady increase in number of successfully invading species and increasing relative abundance of exotics in the regional flora indicated that our longstanding weed control policies and practices were ineffective in abating the invasion process.

At the start of this decade Randy Westbrooks (Westbrooks 1990), now the Invasive Plant Liaison for US Departments of Agriculture and Interior, suggested that an effective national weed strategy should recognize four line of defense:

1. Prevention of problem plants from entering commerce by enactment of treaty, trade agreements, and law.

2. Exclusion by actual port inspection of trade items and persons entering the United States, pure seed certification, weed seed free forage programs and similar quarantine mechanisms.

3. Rapid Response of land management and regulatory agencies to provide early detection, and intervention to attempt eradication, or at least containment of new weeds that have established in the United States.

4. Perpetual Control of wide spread and abundant noxious weeds for which the opportunity to eradicate or contain was lost.

The USDA Animal and Plant Health Inspection Service (APHIS) and other federal and state agencies with regulatory responsibilities for Prevention and Exclusion recognize that these first two line of defense can only interdict a small proportion of problem plant introductions. Federal agency staffing and efforts to implement Prevention and Exclusion need to be increased, but these two lines of defense alone are not going to solve the weed invasion problem to any greater degree than they have solved the drug problem. It is critical that funding be increased to develop mechanisms and coordination for Rapid Response and facilitate the implementation of early detection, eradication and containment strategies. Responsibility for this third line of defense falls primarily to the federal land management agencies, state agriculture departments, and county level weed control districts. Existing state and federal land management agencies provide the framework to implement these Rapid Response actions. They need adequate funding. Responsibility for Perpetual Control falls to the both public and private sector land stewards.

Cost vs. Timing of Intervention

Intervention to prevent spread, including eradication and containment of founder colonies, must be initiated at an early phase in the invasion process (Hobbs and Humphries 1995). Late intervention allows the more successful weeds to become permanent members of the flora over large geographic regions. The total cost of control plus the negative economic and environmental impacts are much higher for late intervention. Furthermore the annual costs of late intervention continue indefinitely into the future. The invasion process can be seen as consisting of four stages, each requiring a different strategic approach to management, as a weed spreads throughout its potential geographic range and finally approaches the carrying capacity of the new region (see two paired figures below).

If regulatory Exclusion is unsuccessful and a new area is colonized, the weed usually exhibits a lag phase during which eradication may be feasible. Once the weed begins to spread at an exponential rate management strategy shifts to controls that might allow suppression of the target species throughout it range. These include development and distribution of insect and plant disease agents and coordinated IPM programs. As the most successful weeds, such as spotted knapweed and leafy spurge, approach the carrying capacity of their new environments we begin to question the effectiveness of species control efforts even with massive resource inputs.

Strategic weed management might be summarized as having the nine sequential elements listed below. Each element is enacted at increasing orders of magnitude in costs.

Alternative land management is the ultimate and highest cost response. It requires changing our expectation of how we utilize the land. The economic, environmental, and social costs can be huge. One example of alternative land use is to cease cattle ranching in eastern Montana and the western Dakotas because of leafy spurge dominance of rangelands, and replace that way of life with a sheep industry.

Threshold to Prevent Spread (Rapid Response)

The role of government in management of the invasion phenomenon must differ from that of individual landowners. Within the boundaries of a single track of land the owner-manager makes an agronomic or even a site specific conservation benefit decision as to what density of a weed can be tolerated and what threshold justifies control. Some agencies, particularly in the western United States, are also "landowners" that manage specific tracts of public land. But agencies have responsibility beyond the individual tracts. It is to prevent spread across ownership or jurisdictional boundaries and reduce the threat of infestation of new sites. The thresholds that trigger deployment of counter measures by government to prevent spread must be lower than the agronomic or conservation thresholds for single tracts (Auld et al. 1978).

INVADERS System for Weed Tracking, Early Alert, and Strategic Management

The INVADERS Database <http://invader.dbs.umt.edu> is an interactive web site that tracks the historic spread of approximately one thousand exotics plants that have invaded the five Pacific northwest states of United States since 1875. Core data include 80,000 distribution records from herbaria, weed identification laboratories, agency survey and other sources. All distribution records have at least county level spacial resolution. Online outputs include county level distribution maps, time lapse spread maps, spread rate curve graphics, lists of exotics by user specified state or county groupings. A custom database engine organized by species has live links to other URL's providing weed pictures, ecology, and management information for individual weeds. Point location records for weeds can be extracted and imported to GIS for predicting potential maximum ranges, determination of habitats at risk to invasion, optimizing searches for new bio-control agents, and other forms of spatial analyses.

The INVADERS web site was designed for ease of use and on decision-making needs identified by weed agency personnel over a nine year period. Funding has been provided by several state agriculture departments and federal land management agencies. Data and in-kind support has been provided by a larger number of western states and federal agencies. The web site has examples of how agencies in the northwestern states have been using INVADERS data for risk assessment, environmental impact statements, selection of target weeds, making legal noxious designations, and various on-the-ground projects.

Taxonomically qualified users can submit new weed reports directly to the INVADERS web site. Their new distribution records are immediately available for inclusion in output graphics and lists. Users can request automatic next morning e-mail notification of new reports of specific weeds to facilitate eradication and containment efforts.

The INVADERS System can be expanded to provide geographic coverage from the current 5 northwestern to the entire United States. The INVADERS national weed tracking design is a three-tiered distributed network consisting of a National Server, several regional Data Stations, and numerous Data Sources. Each regional Data Stations would cover a multi-state area and could receive data from an unlimited number of Data Sources in that region. The current on-line version of INVADERS is an example of a Data Station for a five state region. Having several multi-state Data Stations would allow optimal utilization of regional expertise on weeds, ecology, and management. Data from the regional Data Stations are collated by the National Server. The INVADERS national scale weed tracking system could be built and implemented over a four year period at a cost of approximately 3 million dollars.

Support for On The Ground Eradication and Containment Efforts

Rapid Response based on early detection followed by eradication and containment actions appear to be among the most cost effective strategies for responding to the plant invasion process. The cost of Rapid Response programs must be shared at the highest levels of social organization. The initial economic or environmental benefits to the land steward are small compared to cost, however the benefit gained by the region and nation from avoiding the necessity of Perpetual Control is large. These Rapid Response actions can be best implemented by increasing funding for weed control and coordination efforts by actual federal land managers and state agencies.

Selected Bibliography

Auld, B.A., K.M. Menz, and N.M. Monaghan. 1978/1979. Dynamics of weed spread: Implications for policies of public control. Protection Ecology 1:141-148.

Forcella, F. 1985. Final distribution is related to rate of spread in alien weeds. Weed Research 25:181-191.

Forcella, F. and S.J. Harvey. 1983. Relative abundance in an alien weed flora. Oecologia 59:292-295.

Forcella, F. and S.J. Harvey. 1988. Patterns of weed migration in northwestern U.S.A. Weed Science 36:194-201.

Forcella, F. and J.T. Wood, 1984. Colonization potentials of alien weeds are related to their "native" distributions: Implications for plant quarantine. Journal Australian Institute Agricultural Science 50:36-40.

Hobbs, R.J. and S.E. Humphries. 1995. An integrated approach to the ecology and management of plant invasions. Conservation Biology 9(4):761-770.

Mack. R.N. 1996. Predicting the identity and fate of plant invaders: Emergent and emerging approaches. Biological Conservation 78:107-121.

Rice, P.M. 1999. INVADERS Database System for Weed Tracking, Early Alert, and Strategic Management. University of Montana. http://invader.dbs.umt.edu

Rice, P. M. 1998. Prevention and the INVADERS Database. Proceedings of the Science in Wildland Weed Management Symposium, April 8-10,1998, Denver, Colorado. Bureau of Land Management, National Applied Resource Sciences Center, Denver, CO. p. 31-54.

Rejmanek, M. 1996. A theory of seed plant invasiveness: The first sketch. Biological Conservation 78:171-181.

Reichard, S.H. and C.W. Hamilton. 1997. Predicting invasions of woody plants introduced into North America. Conservation Biology 11:193-203.

Toney, J.C., P.M. Rice, and F. Forcella. 1998. Exotic plant records in the Northwest United States 1950-1996: An ecological assessment. Northwest Science 72(3):198-213.

Westbrooks, R.G. 1991. Plant protection issues. I. A commentary on new weeds in the United States. Weed Technology 5;232-237.