Potential establishment of alien-invasive forest insect species in the United States: where and how many?

Potential Economic Impacts of the Asian Longhorned Beetle (Coleoptera: Cerambycidae) in Eastern Canada

The Asian longhorned beetle (Anoplophora glabripennis Motschulsky) continues to pose a significant risk to deciduous forests around the world. We assess Asian longhorned beetle-related risks in eastern Canada by generating current and future climate suitability maps, import-based likelihood of introduction estimates for each urban center in our study area, and potential economic impacts in both urban and natural settings. For the current period, climatic suitability for Asian longhorned beetle was highest in southern Ontario, but was projected to expand significantly northward and eastward by midcentury. High likelihood of Asian longhorned beetle introduction was associated with large urban centers, but also smaller centers with high levels of pest-associated imports. Potential costs for the removal and replacement of Asian longhorned beetle-impacted street trees ranged from CDN$8.6 to $12.2 billion, with the exact amount and city-level ranking depending on the method used to calculate risk. Potential losses of merchantable maple (Acer) timber were estimated at CDN$1.6 billion using provincial stumpage fees and CDN$431 million annually when calculated using a combination of economic and forestry product statistics. The gross value of edible maple products, which could potentially be affected by Asian longhorned beetle, was estimated at CDN$358 million annually. These values can help inform the scale of early detection surveys, potential eradication efforts, and research budgets in the event of future Asian longhorned beetle introductions.

Current Status of Forest Health Policy in the United States

ederal policies related to forestry and forest health (specifically, insects and diseases) have the potential to affect management practices, terms of international and interstate trade, and long-term sustainability and conservation. Our objectives were to review existing federal policies, the role of federal agencies in managing forest health, and guidance for future policy efforts. Since the 1940s, various federal policies relevant to forest health have been established, and several US Department of Agriculture (USDA) agencies have been empowered to assist with prevention, quarantine, detection, management, and control of insects and diseases. Overall, our review showed that relatively few national policies directly address forest health as a stand-alone objective, as most of them are embedded within forestry bills. Federal funding for forest health issues and the number of personnel dedicated to such issues have declined dramatically for some agencies. Concomitantly, native species continue to gain pestiferous status while non-native species continue to establish and cause impacts in the US. To enhance our ability and capacity to deal with current and future threats, concerted efforts are needed to advocate for both resources and stand-alone policy tools that take seriously the complexity of emerging sustainability challenges in both private and public forestlands.

Important Insect and Disease Threats to United States Tree Species and Geographic Patterns of Their Potential Impacts

Diseases and insects, particularly those that are non-native and invasive, arguably pose the most destructive threat to North American forests. Currently, both exotic and native insects and diseases are producing extensive ecological damage and economic impacts. As part of an effort to identify United States tree species and forests most vulnerable to these epidemics, we compiled a list of the most serious insect and disease threats for 419 native tree species and assigned a severity rating for each of the 1378 combinations between mature tree hosts and 339 distinct insect and disease agents. We then joined this list with data from a spatially unbiased and nationally consistent forest inventory to assess the potential ecological impacts of insect and disease infestations. Specifically, potential host species mortality for each host/agent combination was used to weight species importance values on approximately 132,000 Forest Inventory and Analysis (FIA) plots across the conterminous 48 United States. When summed on each plot, these weighted importance values represent an estimate of the proportion of the plot’s existing importance value at risk of being lost. These plot estimates were then used to identify statistically significant geographic hotspots and coldspots and of potential forest impacts associated with insects and diseases in total, and for different agent types. In general, the potential impacts of insects and diseases were greater in the West, where there are both fewer agents and less diverse forests. The impact of non-native invasive agents, however, was potentially greater in the East. Indeed, the impacts of current exotic pests could be greatly magnified across much of the Eastern United States if these agents are able to reach the entirety of their hosts’ ranges. Both the list of agent/host severities and the spatially explicit results can inform species-level vulnerability assessments and broad-scale forest sustainability reporting efforts, and should provide valuable information for decision-makers who need to determine which tree species and locations to target for monitoring efforts and pro-active management activities.

Expected Timber-Based Economic Impacts of a Wood-Boring Beetle (Acanthotomicus Sp.) That Kills American Sweetgum

American sweetgum trees (Liquidambar styraciflua L. [Altingiaceae]) in China are being killed by a newly discovered wood-boring beetle "sweetgum inscriber" (Acanthotomicus sp.). It has not been detected in the United States yet, but given the extent of trade with Asian countries, eventual arrival of this beetle is a serious concern. The American sweetgum is one of the main hardwood species in the southern United States, and provides several economic and ecological benefits to society. We present the first economic analysis of the potential damage from sweetgum inscriber (SI) to timber-based land values in the southern United States. We modeled economic impacts for a range of feasible SI arrival rates that reflect policy interventions: 1) no efforts to prevent arrival (scenario A, once every 14 and 25 yr), 2) partial prevention by complying with ISPM 15 standards (scenario B, once every 33 and 100 yr), and 3) total prevention of arrival (scenario C, zero transmission of SI). Our results indicated much lower land values for sweetgum plantations without the prevention on SI establishment (scenario A, US$1,843-US$4,383 ha-1) compared with partial prevention (scenario B, US$5,426-US$8,050 ha-1) and total eradication of SI (scenario C, US$9,825). Across the region, upper bound timber-based economic losses to plantation owners is US$151.9 million (US$4.6 million annually)-an estimate that can help inform policy decisions.

Pre-invasion economic assessment of invasive species prevention: A putative ambrosia beetle in Southeastern loblolly pine forests

Invasive wood borers vectoring pathogenic fungi have nearly exterminated several North American tree species, and it is unclear whether landscape dominant trees, such as pines, will face similar threats in the future. This paper explores the economic impacts of a hypothetical arrival of a destructive ambrosia beetle "X" (Coleoptera: Curculionidae) that infests loblolly pine (Pinus taeda L.) forests in the Southeastern United States. We develop an economic framework for pre-invasion assessment that incorporates fluctuating economic and environmental conditions for a representative loblolly pine stand and biological assumptions from the ongoing laurel wilt epidemic. Assuming an initial annual probability of arrival of a pine infesting ambrosia beetle to be between 0.04 and 0.07, we determine that, on average, the timber economic benefits for a forest landowner are $5325.3 ha^-1, with a harvest time of 17.8 years. Our results indicate that an increase in enforcement consistent with an international phytosanitary standard that partially prevents the arrival of ambrosia beetles (30% arrival reduction) would have a strong, positive impact for forest landowners. On average, economic revenues increase to $6116.4 ha^-1 and the harvest age is extended to 19 years. On average, the economic losses for forest landowners with no control of ambrosia beetle X would be $791 ha^-1, with a harvest time reduction of 1.2 years. The upper-bound regional cost savings from pine-dominated forestry would be roughly $4.6 billion dollars if invasion preventative measures are in place. These benefits vastly outweigh the cost of programs that reduce the expected arrival of exotic ambrosia beetles.

Global threats from invasive alien species in the twenty-first century and national response capacities

Invasive alien species (IAS) threaten human livelihoods and biodiversity globally. Increasing globalization facilitates IAS arrival, and environmental changes, including climate change, facilitate IAS establishment. Here we provide the first global, spatial analysis of the terrestrial threat from IAS in light of twenty-first century globalization and environmental change, and evaluate national capacities to prevent and manage species invasions. We find that one-sixth of the global land surface is highly vulnerable to invasion, including substantial areas in developing economies and biodiversity hotspots. The dominant invasion vectors differ between high-income countries (imports, particularly of plants and pets) and low-income countries (air travel). Uniting data on the causes of introduction and establishment can improve early-warning and eradication schemes. Most countries have limited capacity to act against invasions. In particular, we reveal a clear need for proactive invasion strategies in areas with high poverty levels, high biodiversity and low historical levels of invasion.

Globalization facilitates the spread of invasive alien species, while environmental change can ease invasion. Here, Early et al. identify vulnerable regions globally and evaluate capacity in vulnerable countries to prevent invasions arising from sources such as air travel, horticulture, and pet trade.

Bark and Ambrosia Beetles Show Different Invasion Patterns in the USA

Non-native bark and ambrosia beetles represent a threat to forests worldwide. Their invasion patterns are, however, still unclear. Here we investigated first, if the spread of non-native bark and ambrosia beetles is a gradual or a discontinuous process; second, which are the main correlates of their community structure; third, whether those correlates correspond to those of native species. We used data on species distribution of non-native and native scolytines in the continental 48 USA states. These data were analyzed through a beta-diversity index, partitioned into species richness differences and species replacement, using Mantel correlograms and non-metric multidimensional scaling (NMDS) ordination for identifying spatial patterns, and regression on distance matrices to test the association of climate (temperature, rainfall), forest (cover area, composition), geographical (distance), and human-related (import) variables with β-diversity components. For both non-native bark and ambrosia beetles, β-diversity was mainly composed of species richness difference than species replacement. For non-native bark beetles, a discontinuous invasion process composed of long distance jumps or multiple introduction events was apparent. Species richness differences were primarily correlated with differences in import values while temperature was the main correlate of species replacement. For non-native ambrosia beetles, a more continuous invasion process was apparent, with the pool of non-native species arriving in the coastal areas that tended to be filtered as they spread to interior portions of the continental USA. Species richness differences were mainly correlated with differences in rainfall among states, while rainfall and temperature were the main correlates of species replacement. Our study suggests that the different ecology of bark and ambrosia beetles influences their invasion process in new environments. The lower dependency that bark beetles have on climate allowed them to potentially colonize more areas within the USA, while non-native ambrosia beetles, being dependent on rainfall, are typically filtered by the environment.

Exploring critical uncertainties in pathway assessments of human-assisted introductions of alien forest species in Canada

Long-distance introductions of alien species are often driven by socioeconomic factors, such that conventional "biological" invasion models may not be capable of estimating spread fully and reliably. In this study, we demonstrate a new technique for assessing and reconstructing human-mediated pathways of alien forest species entries to major settlements in Canada via commercial road transportation and domestic trade. We undertook our analysis in three steps. First, we used existing data on movement of commodities associated with bark- and wood-boring forest pests to build a probabilistic model of how the organisms may be moved from one location to another through a transportation network. We then used this model to generate multiple sets of predictions of species arrival rates at every location in the transportation network, and to identify the locations with the highest likelihood of new incursions. Finally, we evaluated the sensitivity of the species arrival rates to uncertainty in key model assumptions by testing the impact of additive and multiplicative errors (by respectively adding a uniform random variate or symmetric variation bounds to the arrival rate values) on the probabilities of pest transmission from one location to another, as well as the impact of the removal of one or more nodes and all connecting links to other nodes from the underlying transportation network. Overall, the identification of potential pest arrival hotspots is moderately robust to uncertainties in key modeling assumptions. Large urban areas and major border crossings that have the highest predicted species arrival rates have the lowest sensitivities to uncertainty in the pest transmission potential and to random changes in the structure of the transportation network. The roadside survey data appears to be sufficient to delineate major hubs and hotspots where pests are likely to arrive from other locations in the network via commercial truck transport. However, "pass-through" locations with few incoming and outgoing routes can be identified with lower precision. The arrival rates of alien forest pests appear to be highly sensitive to additive errors. Surprisingly, the impact of random changes in the structure of the transportation network was relatively low.

Community composition and phenology of native Siricidae (Hymenoptera) attracted to semiochemicals in Minnesota

As a result of the introduction of Sirex noctilio F. into North America, there has been increased interest in the poorly-described native Siricidae communities. To date, few studies have surveyed specifically for Siricidae, and many reports of native siricid populations are byproducts of sampling efforts targeting Coleoptera. We report results from a survey targeted specifically at native and exotic Siricidae in Minnesota. We used Lindgren funnel traps from 2006 to 2008 baited with α/β-pinene (Sirex lure), ethanol (EtOH), EtOH + α-pinene, or Ips 3-part lures. We captured 704 native Siricidae comprising seven species, of which none were exotic. To our knowledge, this is one of the largest field collections of Siricidae from a single discrete set of localities in existence. Adult Siricidae began flying in June and continued into October each year. The α/β-pinene lure was most effective, but the EtOH + α-pinene lure was also moderately effective. We compare our data with those from several states and provinces in the Great Lakes Region of North America. Our data provide insight into the community composition of native Siricidae in Minnesota, while concurrently providing evidence that S. noctilio populations have not yet reached this far into the continental United States.