Cover
Title Page
List of contributors
Preface
1. References
CHAPTER 1: Integrating biological control into a conservation context: why is it necessary?
1. Potential problems if integration is lacking
2. Book organization
3. Acknowledgments
4. References
CHAPTER 2: Designing restoration programs based on understanding the drivers of ecological change
1. Overview of concepts
2. Designing a restoration plan using Connecticut River floodplain forests as a model
3. Acknowledgments
4. References
CHAPTER 3: Matching tools to management goals
1. Introduction
2. Eradication
3. Limiting spread
4. Local, or area-wide, temporary suppression of invaders
5. Area-wide, permanent suppression through modification of ecosystem processes
6. Area-wide, permanent control through natural enemy introductions
7. Factors affecting control efficacy
8. Effects of treatment scale on control operations
9. When is biological control the right choice?
10. Key messages
11. Acknowledgments
12. References
CHAPTER 4: Tools in action: understanding tradeoffs through case histories
1. Risk tradeoffs in invasive species management
2. When is no action the right choice?
3. Is herbicide use a good option for invasive plant control?
4. Are biological control projects high or low risk?
5. Acknowledgments
6. References
CHAPTER 5: Benefit–risk assessment of biological control in wildlands
1. Who gets to decide which species are targeted
2. Evidence needed to justify use of biological control
3. What principles and processes should guide decision-making?
4. Risk assessment of biological control agents
5. Post-release risk evaluation
6. Conclusions
7. Acknowledgments
8. References
CHAPTER 6: Systematics and biological control
1. Introduction
2. Identification’s effect on biological control service
3. Using classifications to make biological predictions
4. The importance of voucher specimens
5. Molecular methods
6. Conclusions
7. Acknowledgments
8. References
CHAPTER 7: Forecasting unintended effects of natural enemies used for classical biological control of invasive species
1. Introduction
2. Forecasting non-trophic effects
3. Forecasting unwanted trophic effects
4. Conclusions
5. Acknowledgments
6. References
CHAPTER 8: Measuring and evaluating ecological outcomes of biological control introductions
1. Introduction
2. Setting the stage
3. Defining success in biological control programs
4. Evidence for success or failure
5. Population growth rates and demographic modeling
6. Principles of stewardship
7. Conclusions
8. Acknowledgments
9. References
CHAPTER 9: Methods for evaluation of natural enemy impacts on invasive pests of wildlands
1. Types of outcomes used as measures of impact
2. Evaluation methods for invasive insects
3. Evaluation methods for invasive plants
4. Conclusions
5. Acknowledgments
6. References
CHAPTER 10: Cases of biological control restoring natural systems
1. The value of case histories
2. Successes
3. Failures
4. Projects still unfolding
5. Acknowledgments
6. References
CHAPTER 11: Societal values expressed through policy and regulations concerning biological control releases
1. Introduction
2. National regulatory processes and differences
3. Scientists and regulators: different perspectives
4. Differences in national approaches and associated cultural values
5. Where can process improvements be made?
6. Conclusions
7. Acknowledgments
8. References
CHAPTER 12: Managing conflict over biological control: the case of strawberry guava in Hawaii
1. Introduction
2. Strawberry guava in Hawaii
3. Regulatory review of strawberry guava biological control
4. Lessons learned about our public
5. Lessons learned about the process
6. Conclusions
7. Acknowledgments
8. References
CHAPTER 13: An ethical framework for integrating biological control into conservation practice
1. Why integration of biological control into conservation practice is an ethical issue
2. How environmental thought evolved to encompass classical biological control as an ethical issue
3. Risk, precaution, prudence, and policy
4. A framework to improve ethics of biological control decisions
5. Conclusion
6. Acknowledgments
7. References
CHAPTER 14: Economics of biological control for species invading wildlands
1. Introduction
2. Losses from wildland invaders
3. Benefit: cost ratios for biological control
4. Additional costs of restoration to desired conditions
5. Effects of economic interests on target selection for biological control
6. How should biological control in wildlands be financed?
7. Conclusions
8. Acknowledgments
9. References
CHAPTER 15: The future of biological control: a proposal for fundamental reform
1. Introduction
2. Ethical and normative foundations of stewardship
3. Why is biological control a better choice for pest management?
4. What is the status quo?
5. Assignment of responsibilities
6. Biological control program flow structure
7. Conclusions
8. Acknowledgments
9. References
Concluding thoughts on future actions
Index
End User License Agreement

List of Tables

Chapter 03
1. Table 3.1 Criteria for determining safety and feasibility of invasive species management.
2. Table 3.2 Summary of management options for invasive species.
3. Table 3.3 Steps in classical biological control.
Chapter 04
1. Table 4.1 Biological control projects selected to illustrate a spectrum of risk due to characteristics, not of potential biological control agents, but of the project itself.
Chapter 05
1. Table 5.1 Factors to be considered in choosing a management method for an invasive population.
Chapter 09
1. Table 9.1 Projection matrices, dominant eigenvalues, and elasticity matricies for Carduus nutans at two sites in New Zealand. Reproduced with permission from Shea and Kelly (1998).
Chapter 12
1. Table 12.1 Impacts expected from biological control of strawberry guava.
2. Table 12.2 Significance criteria specified for evaluation in a State of Hawaii Environmental Assessment: an Environmental Impact Statement is required if, to a significant level of expected impact, a project …

List of Illustrations

Chapter 02
1. Figure 2.1 A chart to classify the ecological role of an invasive species on the spectrum from invasion being a consequence of ecological change to invasion being the cause of ecological change.
2. Figure 2.2 Decision tree to assist in determining the strategy that is likely to be most effective at restoring an ecosystem.
3. Figure 2.3 Forlorn TNC intern standing surrounded by Japanese knotweed in a high-gradient river floodplain forest on the Green River in Massachusetts, June 23, 2009.
4. Figure 2.4 Connecticut River floodplain forest breaking down under a heavy load of invasive oriental bittersweet and turning into a weedy vine thicket, West Springfield, Massachusetts, March 15, 2013.
5. Figure 2.5 Tree size distribution for American elm (U. americana) and silver maple (A. saccharinum), the two most common tree species in Connecticut River floodplain forests when surveyed in 2008 to 2011. Note the rapid reduction of elms beyond 20 cm and absence over 60 cm dbh, in contrast to silver maple, likely due to Dutch elm disease.
Chapter 03
1. Figure 3.1 Mechanical removal of non-native gorse (Ulex europaeus) for wildlife habitat improvement at the Coquille Unit of Oregon Islands National Wildlife Refuge, Coos County, Oregon, USA.
2. Figure 3.2 (a) Flightless female gypsy moth, Lymantria dispar; (b) lure traps using female pheromones effectively capture male adult gypsy moths.
3. Figure 3.3 To target individual trees, cuts can be made into the trunk of a tree and a herbicide applied.
4. Figure 3.4 Island Conservation, Parks Canada, and Haida Nation worked together in 2013 to protect Ancient Murrelets by removing invasive rats. This image shows an aerial broadcast of cereal pellets on Murchison and Faraday Islands, Haida Gwaii, British Columbia.
5. Figure 3.5 (a) Treatment area for eradicating Wasmannia auropunctata from a 21 ha area on Marchena Island in the Galápagos Islands archipelago. The inset is a closer view of the 3–4 m grid of bait monitoring stations (Causton et al., 2005); (b) preparation of peanut butter bait sticks for monitoring (up to 44,000 baits were put out in grids).
Chapter 04
1. Figure 4.1 Prescribed fire to control Scotch broom on the Elizabeth Islands, Massachusetts. Scotch broom has invaded maritime grasslands.
2. Figure 4.2 Herbicide application is a common, usually non-selective form of control used against invasive plants. Here, an aerial herbicide application to kill Phragmites australis.
Chapter 05
1. Figure 5.1 Differences by taxon in rates at which intentionally introduced and accidentally introduced species become pests suggest that, for terrestrial vertebrates, fish, and mollusks, deliberate introduction does not lower risk. In contrast, for insects and plant pathogens, categories for which biological control introductions would dominate the intentionally released groups, risk is highly reduced over random introduction. This reduction suggests that biological agent selection seeks safe agents and avoids release of risky species, which is not the case on average for intentionally released species in other taxa (Office of Technology Assessment, 1993).
2. Figure 5.2 Biological control is a method of invasive species management that generally shows high levels of target specificity. Shown here are two brown clumps of purple loosestrife (Lythrum salicaria) selectively defoliated by Galerucella leaf beetles introduced to North America, while all remaining wetland vegetation remains untouched despite food limitation for developing larvae.
3. Figure 5.3 Larvae of Cactoblastis cactorum, an herbivore that attacks various native and pest Opuntia cacti.
4. Figure 5.4 Rhinocyllus conicus, a polyphagous thistle-head feeding insect that is well known to attack a range of native thistles.
5. Figure 5.5 Adult polyphemus moth, Antheraea polyphemus (Cramer), one of the giant silkmoths strongly attacked by the tachinid Compsilura concinnata.
Chapter 06
1. Figures for Box 6.1 Taxonomic errors can contaminate efforts to evaluate the risks associated with a biological control action (or a decision not to take action). Manduca brontes (left) (photo courtesy of Andy Warren) has been treated as a species at risk from the loss of ash, but the species is largely an extralimital, temporary breeder in the continental United States and published reports of the caterpillar feeding on ash were based on no-choice laboratory-reared caterpillars; temporary populations in Florida are believed to use yellow trumpetbush, Tacoma stans (L.). Grant’s Hercules beetle (Dynastes granti) is the largest beetle in the North America with some males approaching 80 mm in length (right) (photo courtesy of Margarethe Brummermann). It and three other rhinoceros beetles appear to be dependent on ash either as larvae (Xyloryctes) or as adults (Dynastes) (Wagner and Todd, 2015, 2016). Previous risk assessments for EAB in North America overlooked these charismatic beetles. See text.
2. Figure 6.1 Haplotype data can be used to identify geographic distributions of invasive organisms. Williams et al. (2007) mapped the probability of having the eastern (left) and western (right) haplotypes of Schinus terebinthifolius in Florida. The identification of these genetic and geographic differences also led to the determination that different haplotypes vary in their susceptibility to a candidate biological control agent, Pseudophilothrips ichnini, which itself appears to represent a cryptic-species complex (Manrique et al., 2008). Williams et al. 2007.
3. Figure 6.2 Cladogram for wax scales. The Chinese wax scale Ceroplastes sinensis was a cosmopolitan pest of citrus at the time it was described by Del Guercio in 1900 (his holotype was collected in Italy). As indicated by its name, Del Guercio assumed the scale to be of Asian origin, but a cladistic analysis by Qin et al. (1994) based on 57 morphological characters, suggested otherwise. In Qin et al.’s (1998) tree, C. sinensis grouped in a clade that contained nine Neotropical wax scales. Subsequent studies suggested the species was native to southern South America, and an expedition to Argentina resulted in the species’ rediscovery as well as parasitoids that were successfully introduced elsewhere. Qin and Gullan 1995.
4. Figure 6.3 Susceptibility of tropical angiosperms to pathogenic fungi correlates with phylogenetic distance. Such relationships across trophic levels demonstrate the value of using phylogenies and classifications to design non-target/specificity studies that can be used to gauge potential non-target impacts that could accrue from the release of a biological control agent.
5. Figure 6.4 Ecological niche modeling (ENM) can be integrated with the results from molecular analyses to identify variation in environmental factors influencing the distributions of candidate biological control agents. Using ENM software, Lozier and Mills (2009) identified different distributions for evolutionary significant units (ESUs) of the parasitoid Aphidius transcaspicus. They then used these results to identify climatic variables that might restrict each of these ESUs and may influence their establishment as biological control agents. Lozier and Mills 2009. Used under CC-BY-4.0, http://creativecommons.org/licenses/by/4.0/.
6. Figures for Box 6.2 Improvements in non-destructive DNA extraction methods are allowing museum specimens to be integrated into molecular analyses with little to no morphological damage to the specimens. Andersen and Mills (2012) extracted DNA from individual museum specimens of Meteorus sp. On the left is a specimen prior to DNA extraction, in the center the specimen placed in a 1.5 ml microcentrifuge tube, and on the right after articulation following DNA extraction. While not visible in the photo, post-extraction specimens appeared slightly translucent compared to pre-extraction specimens.
Chapter 08
1. Figure 8.1 Forests in eastern North America have been transformed by excessive browse of white-tailed deer (Odocoileus virginianus), eliminating forest understories and tree regeneration (Binghamton University forest preserve in New York State, USA).
2. Figure 8.2 Leaf beetles (Galerucella spp.), biological control agents released against purple loosestrife (Lythrum salicaria L.) often eliminate all annual growth, a biological success (here Montezuma wetlands complex in upstate New York). Only if a diverse native flora and fauna replaces purple loosestrife is this biological success also an ecological success.
3. Figure 8.3 Showy displays of the native spring ephemeral Trillium grandiflorum (Michx.) Salisb. were once common in northeastern US forests. The decline in the species has often been associated with non-native plant invasion, but overabundant native deer are a larger demographic threat.
4. Figure 8.4 Permanently marked (note numbered metal tag) Trillium grandiflorum used to assess effects of deer browse on plant demography.
Chapter 09
1. Figure 9.1 Evaluation methods “before/after” combined with “release/control” to measure impacts of the egg parasitoid Gonatatocerus ashmeadi on glassy-wing sharpshooter, Homalodisca vitripennis.
2. Figure 9.2 Changes in density of larch casebearer, Coleophora laricella, in Oregon (USA) over a 25-year period, in relation to the introduction of the parasitoid Agathis pumila, showing a drop in density of approximately 97% in the “after” period as compared to the “before” interval, demonstrating effective and sustained biological control of this pest.
3. Figure 9.3 Use of exclusion cages in the native range (Australia) of cottony cushion scale (Icerya purchasi) to measure impact of the ladybird beetle Rodolia cardinalis.
4. Figure 9.4 Recovery of Pisonia grandis on Cousine Island in the Seychelles after use of ant-baiting to break up mutualism supporting high density of invasive scale: left before baiting; right after baiting.
5. Figure 9.5 Net population growth rates (R₀) of emerald ash borer populations (Agrilus planipennis) estimated from life tables of each observed generation across different study sites in Michigan during the seven-year study (2008–14): solid black line represents R⁰ values when all the observed parasitism (by both introduced parasitoid Tetrastichus planipennisi and all North American parasitoids); long-dashed line represents R₀ values when parasitism by T. planipennisi is absent, and short-dashed line represents R₀ values when all the parasitoid species were absent from the life tables.
6. Figure 9.6 Relationship between seed bank densities and spotted knapweed (Centaurea stoebe L.) density, demonstrating the concept of processes acting with thresholds.
7. Figure 9.7 Relationship over time between density of Sesbania punicea at plots with one (A–C), two (D–F or G–L, each species), or three (M–P) biological control agents, in South Africa.
8. Figure 9.8 Before (left) (1997) and after (right) (1999) control of waterhyacinth (Eichhornia crassipes) at Port Bell on Lake Victoria, Uganda.
9. Figure 9.9 Sample life cycle diagram of Carduus nutans in New Zealand.
10. Figure 9.10 Increase in native plant richness in plots following biological control of mist flower (Ageratina riparia) in New Zealand, where the solid dots are for an invader plot and the hollow dots are for an invaded plot where the weed came under biological control.
Chapter 10
1. Figure 10.1 Melaleuca island in an invaded wetland.
2. Figure 10.2 Few to no plants can survive in the sterile habitat under melaleuca stands.
3. Figure 10.3 The melaleuca weevil, Oxyops vitiosa, destroys seed production by more than 95%.
4. Figure 10.4 (a) The melaleuca psyllid, Boreioglycaspis melaleucae Moore (adult) was the second agent released against melaleuca. (b) Psyllid flocculence, showing a colony of the insect.
5. Figure 10.5 Recovery of native vegetation in a melaleuca-dominated plot, following successful biological control, of melaleuca; note the dead trees and open canopy.
6. Figure 10.6 Decline in melaleuca density and increase in species diversity as biological control agents exerted their effect at a Florida research site.
7. Figure 10.7 Control of mist flower (Ageratina riparia) by the introduced white smut fungus, Entyloma ageratinae, showing the same location (a) about a year after fungus release when plants were infected but not yet killed (January 27, 2000–summer) and (b) two years later when mist flower shrubs had died and been replaced by mostly native vegetation, particularly ferns and grasses (November 8, 2001–spring); site is Brookby on the edge of the Hunua Ranges (an important water catchment and biodiversity area, just southeast of Auckland, New Zealand), and (c) endangered New Zealand endemic plant, Hebe acutiflora Cockayne, no longer threated by mist flower.
8. Figure 10.8 White mangrove infested with cottony cushion scale.
9. Figure 10.9 Endemic Galápagan plants whose populations were threatened by cottony cushion scale: left Darwiniothamnus tenuifolius, and right, Scalesia sp.
10. Figure 10.10 Adult Rodolia cardinalis preying on cottony cushion scale.
11. Figure 10.11 Reduction of cottony cushion scale on white mangrove, on Santa Cruz island, Galápagos, before (2002) and after (2010 and 2011) release of Rodolia cardinalis. Hoddle et al. 2013.
12. Figure 10.12 Walk-in field cage (right) stocked with native plants (left) infested with non-target insects to assess feeding preferences of adult Rodolia cardinalis.
13. Figure 10.13 Rodolia cardinalis larva faced with a choice: cottony cushion scale or Ceroplastes sp. scale (top), attacks the cottony cushion scale (bottom).
14. Figure 10.14 Remnant patch of lowland dry forest, with wiliwili tree, Erythrina sandwicensis, in foreground at Puuwaawaa, Big Island, Hawaii.
15. Figure 10.15 Adult of erythrina gall wasp, Quadrastichus erythrinae (left, photo courtesy of M. Tremblay), and galled leaves from Koko Crater (right, photo credit, Leyla Kaufman).
16. Figure 10.16 Exploration in Madagascar (left, photo credit, Russell Messing) did not yield parasitoids; but additional collections in South Africa, Kenya, and Tanzania were successful, yielding several parasitoid species – including Eurytoma erythinae (right, photo courtesy of Walter Nagamine), which is helping to preserve rare endemic trees in Hawaii.
17. Figure 10.17 Balsam woolly adelgid on trunk (left) and gouty twigs resulting from twig infestation (right).
18. Figure 10.18 Fraser fir killed by balsam woolly adelgid, together with regenerating young trees not yet old enough to be susceptible.
19. Figure 10.19 Lantana invading pastures and native forest understory in southeast Queensland, Australia.
20. Figure 10.20 Lantana defoliated by the tree hopper Aconophora compressa in southeast Queensland, Australia and close up of insect.
21. Figure 10.21 Adults of emerald ash borer, Agrilus planipennis.
22. Figure 10.22 Dead ash, killed by emerald ash borer, lining Michigan roadside.
23. Figure 10.23 Emerald ash borer larvae feeding on ash cambium.
24. Figure 10.24 (a, b) Tetrastichus planipennisi adult and larvae inside host larva, an important parasitoid of emerald ash borer, introduced from China.
25. Figure 10.25 Oobius agrili ovipositing in an emerald ash borer egg; this is another important parasitoid introduced from China.
26. Figure 10.26 Increase in rates of parasitism of emerald ash borer larvae by the introduced parasitoid Tetrastichus planipennisi in Michigan, following its introduction in 2008.
27. Figure 10.27 Parasitism by Tetrastichus planipennisi is limited by bark thickness relative to ovipositor length, such that only smaller trees are protected.
28. Figure 10.28 Miconia leaf, showing injury owing to infestation by the fungal pathogen Colletotrichum gloeosporioides [Penz] Sacc. f. sp. miconiae at Nuku Hiva, Tahiti, 2007.
29. Figure 10.29 Regrowth of native vegetation, including the rare endemic shrub Psychotria (Rubiaceae), in the understory of a miconia invaded forest in Tahiti, with 20% leaf damage on canopy miconia leaves caused by the introduced fungal pathogen Colletotrichum gloeosporioides [Penz] Sacc. f. sp. miconiae.
Chapter 12
1. Figure 12.1 Strawberry guava, Psidium cattleianum, thickets crowd out native forest species in Hawaii.
2. Figure 12.2 Tectococcus ovatus scales make galls on young leaves of strawberry guava.
3. Figure 12.3 Relative frequency of public comments on 2010 Draft Environmental Assessment of proposed biological control of strawberry guava (State of Hawaii, 2011b).
Chapter 13
1. Figure 13.1 Distribution by year of citations of five major articles in the biological control controversy literature.

Preface

The magnitude of threat posed to native ecosystem function and biodiversity by some invasive vertebrates, insects, pathogens, and plants is enormous and growing. At the landscape level, after damaging invaders are beyond eradication, a variety of habitats and ecosystems, on islands and continents, in all parts of the world may be affected and require some form of restoration. Biological control offers substantial opportunity to reduce the damage from invasive insects and plants, two of the most frequent and damaging groups of invasive species.

The purpose of this book is to address a nearly 25-year-old rift (from the seminal article by Howarth [1991]) that opened between conservation/restoration biologists and biological control scientists, particularly in the United States, so that in the future conservation biologists and biological control scientists might work together better to restore native ecosystems damaged by invasive species. The planning for this book originated in an informal meeting of conservation biologists, invasion biologists, and biological control scientists in October 2009, in Sunapee, New Hampshire, following a meeting that year on biological control for the protection of natural areas, held in Northampton, Massachusetts.

The tension between biological control and conservation biology had two causes. The first was that by the 1960s biological control agents introduced earlier to protect grazing or agricultural interests were found attacking native plants and insects in natural areas. More extensive search found other cases of such non-target impacts (Johnson and Stiling, 1996; Louda et al., 1997; Strong, 1997; Boettner et al., 2000; Kuris, 2003), tarnishing the use of biological control for a generation of conservation biologists and restoration ecologists. Any discussion of potential use of biological control agent to mitigate pest problems prompted the question: “What will it eat next if it controls the target?” This question is today routinely asked by undergraduates, graduate students, and the general public, but fails to recognize the dietary restrictions of many biological control agents. Mechanisms of population dynamics exist that cause insects with specialized diets, unlike vertebrates, to lose host-finding efficiency when the density of their prey or host plant declines, resulting in lower realized fecundity and a decrease in population size. Therefore, for specialized biological control agents, the answer to “what will they eat next” is “the same, just less of it as it becomes harder to find.” Others were concerned that agents would attack non-target species due to evolutionary expansion of their host ranges. However, while host shifts do frequently occur over evolutionary time (Stireman, 2005; Barrett and Heil, 2012), such changes have rarely been documented among insects introduced for biological control.

The second reason for the lack of understanding that developed between biological control and conservation/restoration scientists was research compartmentalization, with each group defining itself into its own sub-disciplines, attending different meetings and publishing in different journals. This is true both for conservation/restoration biologists (who publish in Conservation Biology, Restoration Ecology, Biological Invasions, etc.) and biological control scientists (BioControl, Biological Control, Biological Control Science and Technology, etc.). Opportunities to talk at length between these groups were, therefore, rare.

If invasive species were not one of the most important drivers of ecological degradation across natural ecosystems, the status quo could continue indefinitely. But they are and we must confront them as efficiently as possible. Conservation biologists should no longer leave a good tool unused and biological control scientists should no longer work in isolation from conservation biologists with special knowledge of the invaded ecosystems. The goal of this book is to discuss these issues in ways that make sense to both groups and find ways to work together better.

References

Barrett, L. G. and M. Heil. 2012. Unifying concepts and mechanisms in the specificity of plant-enemy interactions. Trends in Plant Science 17: 282–292.
Boettner, G. H., J. S. Elkinton, and C. J. Boettner. 2000. Effects of a biological control introduction on three nontarget native species of saturniid moths. Conservation Biology 14: 1798–1806.
Howarth, F. G. 1991. Environmental impacts of classical biological control. Annual Review of Entomology 36: 485–509.
Johnson, D. M. and P. D. Stiling. 1996. Host specificity of Cactoblastis cactorum (Lepidoptera: Pyralidae), an exotic Opuntia-feeding moth, in Florida. Environmental Entomology 25: 743–748.
Kuris, A. M. 2003. Did biological control cause extinction of the coconut moth, Levuana iridescens, in Fiji? Biological Invasions 5: 133–141.
Louda, S. M., D. Kendall, J. Connor, and D. Simberloff. 1997. Ecological effects of an insect introduced for biological control of weeds. Science 277 (5329): 1088–1090.
Stireman, J. O. 2005. The evolution of generalization? Parasitoid flies and the perils of inferring host range evolution from phylogenies. Journal of Evolutionary Biology 18: 325–336.
Strong, D. R. 1997. Fear no weevil? Science (Washington) 277 (5329): 1058–1059.

CHAPTER 1
Integrating biological control into a conservation context: why is it necessary?

Kevin M. Heinz¹, Roy G. Van Driesche², and Daniel Simberloff³

¹ Department of Entomology, Texas A & M University, USA

² Department of Environmental Conservation, University of Massachusetts, USA

³ Department of Ecology & Evolutionary Biology, University of Tennessee, USA

Potential problems if integration is lacking

The basic argument of this book is that, for pests of wildlands¹, biological control should be one of the tools considered for use. Not to do so would lead to inadequate restoration for many pests because, while they might be controlled in small areas, they would remain uncontrolled over much of the landscape. We further argue that biological control will be done better if integrated into conservation biology because that will force greater consideration of the role of the invader as the true source, or not, of ecosystem degradation (see Chapter 2) and would incorporate into the control program more detailed knowledge of the invaded community’s ecology, which may exist best within the conservation biology community. Finally, we argue that biological control in areas of conservation importance can be done safely with modern methods of evaluation for assessing pest impact and natural enemy host range.

When conservation biologists seek to restore natural communities damaged by invasive species, if they give no thought to biological control, their efforts may be far less successful. Without biological control in the mix of potential tools, restoration efforts move toward eradication if possible, suppression over large areas by changing processes (e.g., fire, flood, or grazing regimes) at the landscape level if relevant, or suppressing the invader on small patches with chemical or mechanical tools if these methods work and money can be found for long-term management. Many invaders, however, cannot be eradicated if they are widespread, or their biology may not be appropriate to control over the long term with pesticides or mechanical tools. Similarly, while some plants or insects may have become highly invasive because people have altered historical landscape processes (MacDougall and Turkington, 2005), this factor surely does not account for the damage caused by some invaders. Certainly, it applies to few if any invasive insects: virtually none of the invasive insects that have so damaged North American forests (Campbell and Schlarbaum, 1994; Van Driesche and Reardon, 2014) could be said to have such factors driving their destructive effects. In contrast, some invasive plants quite likely are augmented in their densities by such forces, but clearly not all are. This leaves many highly damaging insects and plants for which restoration of ecological processes toward historical norms will not lead to restoration of the ecosystem. In such cases, then, restoration efforts are limited to saving fragments through intensive efforts at the preserve rather than the landscape level. While these efforts may protect rare species with small, threatened ranges, they do nothing to preserve average habitat conditions for the bulk of species across the broader landscape. Working with biological control scientists can sometimes provide a solution that can safely (if well conceived and executed) protect the landscape rather than just a few isolated preserves.

To succeed at biological control is not easy and requires cross-disciplinary collaborations to understand fully the implications of releasing natural enemies of the invader. If such collaborations with conservation biologists are lacking, decisions may be taken that undervalue certain native species, miss important ways in which these species are interacting, or fail to consider fully the potential impacts of the introduced biological control agents on the native ecosystem or what other forces may be at work driving ecosystem change. If biological control scientists work within a broader restoration team that includes conservation biologists, these potential pitfalls are more likely to be recognized and avoided.

Carrying out a biological control program typically requires a commitment to travel to the invader’s native range and determine what natural enemies affect the invader’s population dynamics there and which of these are plausibly sufficiently specialized that they might be safe for release in the invaded region. These demands require training in natural enemy biology and population dynamics, as well as knowledge of foreign cultures and geography. If the targeted invader is a plant, the biological control scientist must also have extensive understanding of plant taxonomy, physiology, and how both biotic and abiotic factors affect plant demography. If the invader is an insect, the practitioner must also be familiar with the taxonomy and biology of parasitoids or predators, how to rear them, and how they overcome host defenses. Training in these diverse subjects may leave little time to develop a deep appreciation for the community ecology and details of the particular ecosystems invaded by the pest. This leaves the biological control scientist vulnerable to making decisions that fail to take such information fully into account, and hence underscores the value of collaborative projects within a conservation biology framework, working with specialists on the ecology of the invaded communities.

Book organization

The practices of biological control and ecological restoration can be viewed as large-scale field experiments that unintentionally test many fundamental principles in ecology, as noted previously for both biological control (e.g., Hawkins and Cornell, 1999; Wajnberg et al., 2001; Roderick et al., 2012) and species conservation and habitat restoration (e.g., Young, 2000; Groom et al., 2005). Several issues need addressing when one attempts to integrate biological control of pests of wildlands into the larger framework of conservation biology. In the chapters that follow, experts illustrate some of the problems that can arise when such integration is lacking and provide insights for avoiding problems that may affect the management program or conservation interests.

In Chapter 2, readers are presented with a conceptual framework for confirming whether an invasive species is the primary cause of environmental change and for deciding how to minimize its impacts, potentially as part of a larger package of restoration activities. Approaches potentially able to generate the desired outcomes are discussed and illustrated with the example of conservation threats to floodplain forests in New England. Chapter 3 subsequently addresses the means (tools) available to control invasive species. Depending on circumstances, control goals may be eradication, human-sustained invader suppression with periodic mechanical or chemical control plus monitoring, or permanent area-wide invader suppression through alteration of ecosystem processes or programs of biological control. Once goals are set, a variety of tools may be relevant and are discussed (mechanical, chemical, biological, combinations) in terms of the system or pest attributes that affect efficacy, control cost, and effects on the environment. Chapter 4 examines tradeoffs among risks posed by major control methods using case histories of particular projects. Chapter 5 continues this discussion through an examination of how the risks and benefits of biological control projects against wildland pests can best be recognized and compared, through the planned interaction of biological control scientists and conservation biologists. At the end of these chapters, readers should have a better understanding of when biological control may be the right or wrong option.

The next block of chapters shifts to the practice of biological control within the context of environmental restoration projects. Chapter 6 discusses the importance of systematics and accurate taxonomic identification, both of pests and natural enemies, for biological control programs. The discussion includes recent developments in molecular techniques applicable to modern biological control programs. Chapter 7 addresses our ability to forecast unwanted impacts of biological control, describing the nature of the concern, reviewing the historical record, and ending with a discussion of unresolved issues. Chapters 8 and 9 discuss how to measure and evaluate outcomes of biological control projects. Because biological control is costly in terms of financial and human resources, there is an increasing demand for accountability as to efficacy when biological control is used to restore or protect native ecosystems or species. Addressed directly in these chapters are the difficult tasks associated with delineating the damaged system’s starting conditions and measuring the progress toward achieving restoration goals. Chapter 8 takes a broad conceptual view of the task, while Chapter 9 reviews techniques used for such assessments and their limits and requirements for application. Chapter 10 discusses a series of biological control projects conducted in wildland ecosystems. These cases provide concrete examples of the kinds of damage that can be corrected with biological control, and the discussions of project details highlight the variety of issues that can affect such work.

Concluding chapters address societal and economic matters. Chapter 11 discusses laws and regulations that affect biological control. The evolution of regulations and regulatory agencies from several parts of the world are reviewed, which provides the context for recommendations for improvements in biological control regulations. Chapter 12 describes how conflicts among groups may arise during a biological control project. The focus of the chapter is on methods for setting goals and resolving disagreements that are either initially present or arise during the conduct of the project. Chapter 13 discusses ethical principles related to the introduction of non-native species, focusing on processes and goals that can help resolve disagreements among parties in conflict. In Chapter 14, we discuss economic issues associated with species invasions and their biological control in wildlands. Chapter 15 describes steps to reform the practice of biological control and integrate its use against pests of wildlands into a conservation framework. It also makes recommendations for changes needed to make biological control of agricultural and ornamental pests at least environmentally neutral.

We end by returning to the central message of the book, looking to the future and describing activities likely to further the integration between biological control activities and those of conservation biologists and restoration ecologists.

Acknowledgments

We thank Bernd Blossey, Charlotte Causton, and David Wagner for reviewing Chapter 1.

References

Campbell, F. and S. E. Schlarbaum. 1994. Fading Forests I. Natural Resource Defense Council. New York.
Groom, M. J., G. K. Meffe, and C. R. Carroll. 2005. Principles of Conservation Biology, 3rd edn. Sinauer Associates. Amherst, Massachusetts, USA.
Hawkins, B. A. and H. V. Cornell. 1999. Theoretical Approaches to Biological Control. Cambridge University Press. New York. 424 pp.
MacDougall, A. S. and R. Turkington. 2005. Are invasive species the drivers or passengers of change in degraded ecosystems? Ecology 86: 42–55.
Roderick, G. K., R. Hufbauer, and M. Navajas. 2012. Evolution and biological control. Evolutionary Applications 5: 419–423.
Van Driesche, R. G. and R. Reardon (eds.). 2014. The Use of Classical Biological Control to Preserve Forests in North America. FHTET 2013-2 September 2014. USDA Forest Service. Morgantown, West Virginia, USA.
Wajnberg, E., J. K. Scott, and P. C. Quimby (eds.). 2001. Evaluating Indirect Ecological Effects of Biological Control. CABI Publishing. New York. 261 pp.
Young, T. P. 2000. Restoration ecology and conservation biology. Biological Conservation 92: 73–83.

References

Potential problems if integration is lacking

Book organization

Acknowledgments

References

Note