Stable Coexistence of an Invasive Plant and Biocontrol Agent: A Parameterized Coupled Plant-Herbivore Model

1. Coupled plant-herbivore models, allowing feedback from plant to herbivore populations and vice versa, enable us to predict the impact of biocontrol agents on their target weed populations; however, they are rarely used in biocontrol studies. We describe the population biology of the invasive plant Echium plantagineum and the weevil Mogulones larvatus, a biocontrol agent, in Australia. In order to understand the dynamics of this plant-herbivore system, a series of coupled models of increasing complexity was developed. 2. A simple model was extended to include a seed bank, density-dependent plant fecundity, competition between weevil larvae and plant tolerance of herbivory, where below a threshold plants could compensate for larval feeding. Parameters and functional forms were estimated from experimental and field data. 3. The plant model, in the absence of the weevil, exhibited stable dynamics and provided a good quantitative description of field densities before the weevil was introduced. 4. In the coupled plant-herbivore model, density dependence in both plant fecundity and weevil larval competition stabilized the dynamics. Without larval competition the model was unstable, and plant tolerance of herbivory exacerbated this instability. This was a result of a time delay in plant response to herbivore densities. 5. Synthesis and applications. The coupled plant-herbivore model allowed us to predict whether stable coexistence of target plant and biocontrol agents was achievable at an acceptable level. We found this to be the case for the Echium-Mogulones system and believe that similar models would be of use when assessing new agents in this and other invasive plant biocontrol systems. Density dependence in new biocontrol agents should be assessed in order to determine whether it is likely to result in the aims of classical biocontrol: low, stable and sustainable populations of plant and herbivore. Further work should be done to characterize the strength of density dependence according to the niche occupied by the biocontrol agent, for example the strength and functional form of density dependence in stem borers may be quite different to that of defoliators

Environmental weed control policy in Australia: current approaches, policy limitations and future directions

Plant invasions of natural systems threaten biodiversity and ecosystem processes across many biomes. Historically most plant invasions have been facilitated by human activities such as industry, transport and landscape modification. Consequently, both causes and management of weed invasion are dependent on human behaviour and management advice provided by ecologists needs to take account of this fact. This paper assesses current environmental weed control policy in Australia and asks: are government, land managers and the scientific community using available social levers to achieve optimal weed management? We do this by comparing aspects of weed policy with a generalized natural resource policy framework. Adequacy of issue characterization and policy framing are discussed with particular reference to public perceptions of the weed problem, policy scaling and defining policy principles and goals. The implementation of policy Instruments, including regulation, VOluntary incentives, education, Information, motivational instruments, property-right instruments and pricing mechanisms are reviewed. Limitations of current instruments and potential options to improve instrument effectiveness are discussed. Funding arrangements for environmental weed control are also reported: environmental weed invasion generally represents an external cost to economic markets which has resulted in relatively low funding levels for control operations. Finally, review and monitoring procedures in weed programmes and policy are addressed. Rigorous monitoring systems are important in effective, adaptive weed management where control techniques are continually refined to improve ecological outcomes. The utility of maintaining links between project outcomes and policy inputs along with methods of implementing appropriate monitoring are discussed. </jats:p

A Rosetta Stone For Nature’s Benefits To People

After a long incubation period, the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) is now underway. Underpinning all its activities is the IPBES Conceptual Framework (CF), a simplified model of the interactions between nature and people. Drawing on the legacy of previous large-scale environmental assessments, the CF goes further in explicitly embracing different disciplines and knowledge systems (including indigenous and local knowledge) in the co-construction of assessments of the state of the world’s biodiversity and the benefits it provides to humans. The CF can be thought of as a kind of “Rosetta Stone” that highlights commonalities between diverse value sets and seeks to facilitate crossdisciplinary and crosscultural understanding. We argue that the CF will contribute to the increasing trend towards interdisciplinarity in understanding and managing the environment. Rather than displacing disciplinary science, however, we believe that the CF will provide new contexts of discovery and policy applications for it.131Perrings, C., Duraiappah, A., Larigauderie, A., Mooney, H., The Biodiversity and Ecosystem Services Science-Policy Interface (2011) Science, 331, pp. 1114-1139Brooks, T., Lamoreux, J., Soberón, J., IPBES ≠ IPCC (2014) Trends in Ecology & Evolution, 29 (10), pp. 543-545Sutherland, W.J., Gardner, T.A., Haider, L.J., Dicks, L.V., How can local and traditional knowledge be effectively incorporated into international assessments? (2013) Oryx, 48, pp. 1-2Turnhout, E., Bloomfield, B., Hulme, M., Vogel, J., Wynne, B., Listen to the voices of experience (2012) Nature, 488, pp. 454-455Tengö, M., Brondizio, E., Elmqvist, T., Malmer, P., Spierenburg, M., Connecting Diverse Knowledge Systems for Enhanced Ecosystem Governance: The Multiple Evidence Base Approach (2014) AMBIO, pp. 1-13(2005) Ecosystems and Human Well-Being: SynthesisCarpenter, S.R., Mooney, H.A., Agard, J., Capistrano, D., DeFries, R.S., Science for managing ecosystem services: Beyond the Millennium Ecosystem Assessment (2009) Proceedings of the National Academy of Sciences of the United States of America, 106, pp. 1305-1312Trainor, S.F., Realms of value: Conflicting natural resource values and incommensurability (2006) Environmental Values, 15, pp. 3-29Martin-Lopez, B., Montes, C., Benayas, J., The non-economic motives behind the willingness to pay for biodiversity conservation (2007) Biological Conservation, 139, pp. 67-82Kumar, P., (2010) The Economics of Ecosystems and Biodiversity Ecological and Economic FoundationsWegner, G., Pascual, U., Cost-benefit analysis in the context of ecosystem services for human well-being: A multidisciplinary critique (2011) Global Environmental Change-Human and Policy Dimensions, 21, pp. 492-504Chan, K.M.A., Guerry, A.D., Balvanera, P., Klain, S., Satterfield, T., Where are Cultural and Social in Ecosystem Services? A Framework for Constructive Engagement (2012) Bioscience, 62, pp. 744-756Daniel, T.C., Muhar, A., Arnberger, A., Aznar, O., Boyd, J.W., Contributions of cultural services to the ecosystem services agenda (2012) Proceedings of the National Academy of Sciences of the United States of America, 109, pp. 8812-8819Gilbert, N., “Life on Earth” project gets under way (2014) Nature, p. 455Vanbergen, A.J., Baude, M., Biesmeijer, J.C., Britton, N.F., Brown, M.J.F., Threats to an ecosystem service: pressures on pollinators (2013) Frontiers in Ecology and the Environment, 11, pp. 251-259Garibaldi, L.A., Steffan-Dewenter, I., Winfree, R., Aizen, M.A., Bommarco, R., Wild pollinators enhance fruit set of crops regardless of honey bee abundance (2013) Science, 339, pp. 1608-1611Gonzalez-Varo, J.P., Biesmeijer, J.C., Bommarco, R., Potts, S.G., Schweiger, O., Combined effects of global change pressures on animal-mediated pollination (2013) Trends in Ecology & Evolution, 28, pp. 524-530Scholes, R.J., Reyers, B., Biggs, R., Spierenburg, M.J., Duriappah, A., Multi-scale and cross-scale assessments of social-ecological systems and their ecosystem services (2013) Current Opinion in Environmental Sustainability, 5, pp. 16-25Ludwig, J., Stafford-Msith, M., Interpreting and correctingcross-scale mismatches in resilience analysis: a procedure and examples from Australia’s rangelands (2005) Ecology and Society, 10, p. 20Díaz, S., Demissew, S., Joly, C., Lonsdale, W., Ash, N., The IPBES Conceptual Framework—connecting nature and people (2015) Current Opinion in Environmental Sustainability, 14, pp. 1-16http://www.ipbes.net/images/documents/plenary/second/working/2_17/Final/IPBES_2_17_en.pd