Mark Lonsdale, Richard Mack - Programme Leaders

We contend that the status of biotic invasions is based on a largely anecdotal (and decidedly limited) record of the distribution of invaders world-wide. As a result, the status of these invaders is almost undoubtedly a substantial underestimate of their current role and a poor basis for prediction. Thus, a robust, quantitative argument on the importance of these species, i.e., the type that would attract the global political and financial attention it deserves cannot yet be assembled. The situation for the biosphere is fairly (if indelicately) analogous to a person known to be debilitated by disease(s) but without benefit of knowing which organs have already been attacked, the extent of the infection in those organs, the status of the pathogens' populations (whether expanding, declining), the fate of as yet uninfected organs, and with only a murky understanding of even the causative agents.

As a contribution toward building a comprehensive view of invasions this section will (1) prepare a worldwide assessment of the status of invasions, including an estimate of the ice-free land mass now dominated by plant invaders, (2) identify various scales of detection (and sensitivity) that are currently available (i.e., scaling up from records of individual plants to permanent plot averages (for plants and animals), to larger, less precise estimates of alien status, (3) identify existing methods (and where necessary develop new methods) by which invasions can be rapidly and routinely reassessed. Item (3) will likely include recommendations on the standardization of methods for achieving reassessment routinely in the future. (4) Evaluate existing, largely qualitative methods for monitoring the alien species that are not yet deemed invaders.

In addition to any roles that invaders play in their new ranges, the term "invasions" strongly and correctly implies the occupation of space (i.e., a new range) by these alien organisms. We propose to take initially a spatial view of invasions as a first approximation of their status in a new range, i.e., these organisms' presence can be expressed in map form, at any scale. Inextricably linked to the occupation of space are other indices of these alien organisms that can be represented in a spatial context: e.g. density, biomass/unit area, cover or volume/ unit area (or volume). When viewed in this manner, each of these indices gives a revealing impression of the status of the invader in its new range. Such visual impressions have the advantage of being readily (even instantaneously) interpretable. Thus, much information on the status of an invader can be conveyed and interpreted quickly. Moreover, such assessments can also convey the changing status of invaders spatially over time.

Activities:

(1) Prepare a worldwide assessment of the status of invasions, including an estimate of the ice-free land mass now dominated by plant invaders.

Current information from which a global portrayal could be formed is at best scattered but more likely incomplete and largely anecdotal. Least available are quantitative assessments of the status of alien species across landscapes. For example, we know the spatial distribution of some alien species with reasonable detail, e. g. the distribution of alien members of the British flora as reported by at least one record within 10-km squares of the National (U.K.) grid (e.g. Gilbert 1995, Tiley et al. 1996). Unfortunately, maps of alien species distribution with this detail are rare. A certainly acceptable scale has been prepared for several hundred alien plant spp. in Australia. Parsons and Cuthbertson (1992) prepared dot maps at roughly a 50 x 50 km scale (0.5 degree squares). More commonly however, we have generalized maps of alien distribution that are diffuse at their boundaries and internally "holey", i.e., the map circumscribes a new range in which the alien is found but it is understood that it does not occupy the entire space circumscribed (Salisbury 1961, Mack 1981, Lonsdale 1993, Humphries et al. 1991). Another large category of maps exist only in the most generalized sense - the alien is described as occurring within areas circumscribed by political boundaries (states, provinces, districts, counties) (e.g. records of distribution in Floras). Such portrayals are likely to be so crude as to be potentially mis-leading.

Despite the limitations cited above, authors in this section will be asked to compile continental-level maps (e.g. 1: 500,000- 1:1,000,000) that record mapped invasions. We recognize that these maps will initially have large "blank spaces", but these areas nevertheless need to be identified as the objects of further inquiry. Once completed, these maps will form a basis for comparisons in the future, e. g., to allow reassessment of the spread (contraction, no change) of invaders over decadal intervals. We contend that conservatively-conducted assessments world-wide of the status of aliens will reveal a much larger and more extensive role for these species than is usually perceived. For example, in one preliminary assessment, Mack (1996) determined that at least 3.1% of the earth's ice-free terrestrial area (4.02 x 106 km2) is now dominated by alien plants. This estimate is almost certainly a substantial underestimate, as it does not include invasions in interior Africa, Asia, and most of Europe. Currently, there is no direct manner by which to arrive at an accurate value for this status. Furthermore, for a much larger area plant invasions are prominent locally but not dominant in the once-natural communities. The means by which this undoubtedly large, but diffuse area can be estimated remain problematical.

(2) Identify the various scales of detection (and sensitivity) that are currently available (i.e., scaling up from records of individual plants to permanent plot averages (for plants and animals), to larger, less precise estimates of alien status

We recognize that maps of alien species at different scales serve different purposes. One valuable consequence of the growth of plant demography in the last 25 years has been the production of many maps of individual plants within populations; some of these deal with alien species (Mack & Pyke 1984). In concept, such maps form the ideal for an assessment, since the mapping sites could be recensused repeatedly. Unfortunately, the labor involved in preparing such maps limits their widespread use and the populations may have destroyed at the end of the study.

The records from permanent plots may provide the next level of detection of the status of invasions - plot averages of these species' roles (e.g. density, cover, biomass, volume estimates). The array of permanent plots worldwide is poorly compiled but likely to be extensive. Recent publication of a directory of permanent plots for 27 counties available from the U.S. MAB program may serve as one initial guide to this plot information (ACCESS 1996). An additional guide is available for permanent plots in the U.S. that was prepared for the Ecological Society of America (the FLED committee). Included within these records are current permanent plots within the LTER system in the U.S. These sites include plots that are routinely monitored. Even though not established expressly for following the fate of alien plants, alien plants have been likely included within the mapped populations. Furthermore, these plots are ideal for detecting subsequent entry of alien plants. Despite the litany of limitations within these plot data, we believe that this form of assessment will need to be employed.

Among the coarsest grain estimates of invasions will be those derived from Remote Sensing (Roughgarden et al. 1991). To our knowledge, this approach is unevaluated for the specific purpose of gauging invasions and clearly has intrinsic limitations of detection. Nevertheless, we believe that in some circumstances (e.g. gauging the status of mat-forming aquatic plants, alien trees in a grassland or savanna, the conversion of forest to alien grass-dominated communities) this approach may prove useful. We will invite an authority on GIS to participate in this section's writing effort.

(3) Identify existing methods (and where necessary develop new methods) by which invasions can be rapidly and routinely reassessed.

This topic has both qualitative and quantitative components. The qualitative component is largely covered under (4) since there is a need for rapid surveys in which only the "presence" of alien species is being routinely re-assessed. Another goal of this section is to assess the quality of the maps that are available for alien species and to make recommendations on standardizing map quality. We will systematically assemble and evaluate the available maps of alien invasions. This process will serve at least two purposes. (1) It is the only practical manner in which to begin evaluating the current status of invaders - however imperfect or incomplete the available information. (2) It also serves as a guide from which we can form recommendations for standardized maps for the future. In the many cases in which no status has been assessed and no map exists, we will attempt to form one. The impetus for this effort is the observation that invasions, particularly plant invasions, have often been minimized if not overlooked altogether.

(4) Evaluate existing, largely qualitative methods for monitoring the alien species that are not yet deemed invaders.

This topic potentially overlaps with other sections. Our concern here is to identify examples in which alien species have been detected that have not yet reached invasion status. We know many species deserve to be placed on a "watch list", i.e., they may occur in a new range, may even be naturalized, but have not yet reached (or never may reach) invasion proportions or effect. Although such species may be detected in permanent plots, the likelihood of such detection early is poor. Instead, we advocate qualitative censuses in which alien (both terrestrial and aquatic) species are routinely searched for within a landscape, waterway, coastline. Such a system has been advocated before (OTA 1991) but not implemented nationally within the U.S. Individual U.S. states however have implemented such systems with considerable success, e.g. Idaho (Old et al. 1988). Australia has developed a much more extensive and comprehensive system of early detection, particularly along its northern coastline. In this system, teams of taxonomists routinely search for alien pests, even extending their search into Papua New Guinea. This system has been eminently successful, leading for example to the early detection of Chromolaena odorata, an extremely aggressive Neotropical shrub, in northern Queensland (Anon. 1996).

Outcomes

1. An edited volume (with contributed chapters by the section participants) will be produced (see participant list for listing of tentative chapter topics). We envision a book with 15-17 chapters illustrating and synthesizing comprehensive use of different tools (methods, procedures, scales) for assessing the distribution and status of invaders across broad geographic contexts and taxonomic groups.

2. Readily interpretable multi-color maps of the world-wide distribution of invasions (where feasible). We envision these maps as stand-alone publications with accompanying text containing abbreviated accounts from the edited volume, similar in format to Kuchler's (1964) detailed national and regional vegetation maps of the U.S.

3. Contributions to the Strategic Document. Distillations of (1) and (2) will be contributed to the Strategic Document.

4. Contributions to the Action Plan. Distillations of (1) and (2) will be contributed to the Action Plan.

5. As an instrument of capacity-building, we envision placing the maps and accompanying text (item 2) in at least some abbreviated form on a WEB page. It is likely that in time, the full detail of these maps may be made available in this manner. The development of these sites is readily available at Washington State University.

6. As a further instrument of capacity-building, we will pursue the development of a training grant proposal within the U.S. for the use of Peace Corps volunteers and other government trainees who will need extensive knowledge of this information.

Beneficiaries

We envision these products will be of broad use by a diverse array of investigators and organizations. These include the following.

UNEP and its auxiliary agencies within the UN. All these products will be essential for accurately identifying the sites of current and future invasions. Such prediction is particularly important for the enhancement of commerce and human health and protection of the environment in developing nations. One direct benefit will be the ability to predict and quantify the scale of these threats to World Heritage Sites, both current and pending.

Federal (i.e., national) governmental agencies. Agencies, ministries, federal services require accurate information on the current status of invasions within their holdings. In the United States, for instance, federal lands (and waterways) subject to biotic invasions are administrated by an uncoordinated array of agencies (e.g. the Forest Service, National Park Service, Department of Energy, Bureau of Indian Affairs, Bureau of Land Management, Soil Conservation Service, Department of Defense). In general they have a poor (or at least uneven) understanding of even the most prominent invasions within their land holdings. Consequently, they are in a poor position to estimate the costs of invasions, much less prescribe effective means of control. The products of this section will provide the first spatial context for their management of these lands.

Sub-federal agencies (state, provincial, district level). Obviously, the need for the products to emerge from our section is not restricted to national agencies. Agencies or governments at practically any level of jurisdiction will benefit from more accurate knowledge of the current and potential status of invasions within their holdings. For example, the agencies responsible for the proper management of water resources, such as Water Control Boards in the U.S. These agencies often have broad powers to control (and divert) the flow of water for irrigation, navigation and metropolitan consumption. These decisions affect the spread and proliferation of aquatic invaders. Knowing in advance the status and potential of such invaders regionally would be a powerful management tool.

World Bank, USAID (and regional equivalents). As a major facilitator of economic growth, organizations such as the World Bank have often been criticized as myopic to the environmental (and ultimately long-term economic) consequences of projects they have sponsored. The inadvertent introduction, facilitation and growth of biotic invasions have been negative consequences of their action. Knowledge of the current and potential threat of biotic invasions within a region could (should) readily become an instrument in the planning of World Bank projects (e.g. early consideration of the spread of alien aquatic vascular plants with the impoundment resulting from a hydroelectric dam, similar consideration of the consequences of constructing an all-weather road system in a heretofore isolated region with the attendant opportunity for the spread of alien spp.).

Peace Corps, VOS (and equivalents). Many agencies are involved in training personnel for international service in developing countries. Although this training now often involves land reclamation and sustained agro-forestry, there is an equally compelling argument for personnel to become involved in the control of biotic invaders. Obviously, part of any such future effort will require that the agencies have prior knowledge of the regions in which the demand for such service is high. Thus, knowing the status of these invasions will help direct these control efforts.

Private Conservation Organizations (e.g. World Wildlife Fund, The Nature Conservancy). Given the recognized threat of invasions to biodiversity, these organizations are keenly interested in the status of invasions. Not only will the products of this section reveal invasions that are potential threats to already endangered species, but the maps would also influence decisions on the conservation of other potentially endangered species and the creation of future reserves.

Industry

Biotic invasions present serious hazards to the economic health of natural resource-based industries; knowing the status and character of invasions in a region would readily influence the scope of a financial investment or even whether an investment should be made at all. Two categories of industries are clearly affected by invasions and will be subject increasingly to these phenomena: international timber enterprises and international (as well as large regional) livestock companies. Timber (and fiber) production is becoming the domain of large multi-national corporations [Macmillan-Bloedel, Weyerhauser, Wimpco (Swedish Match), Trillium, Fletcher-Challenge]. Livestock production is also being practiced at a multi-national level (e.g. King Ranch) or large regional operators (King Ranch, Parker Ranch). Such companies own hundreds of thousands of square kilometers. The form of development these companies pursue has major implications for the spread and proliferation of biotic invasions. In addition, these enterprises will need the information from this section to protect their investments, even if they are not initially compelled to deal with invasions through a commitment to protecting the environment.