Ecosystem Viable Yields

The World Summit on Sustainable Development (Johannesburg, 2002) encouraged the application of the ecosystem approach by 2010. However, at the same Summit, the signatory States undertook to restore and exploit their stocks at maximum sustainable yield (MSY), a concept and practice without ecosystemic dimension, since MSY is computed species by species, on the basis of a monospecific model. Acknowledging this gap, we propose a definition of "ecosystem viable yields" (EVY) as yields compatible i) with guaranteed biological safety levels for all time and ii) with an ecosystem dynamics. To the difference of MSY, this notion is not based on equilibrium, but on viability theory, which offers advantages for robustness. For a generic class of multispecies models with harvesting, we provide explicit expressions for the EVY. We apply our approach to the anchovy--hake couple in the Peruvian upwelling ecosystem

Indigenous Knowledge and Sustainable Development: The Case of Rwanda's Agricultural Sector.

The need for creating sustainable and relatable development projects has placed a sharp focus of the different approaches and methods of achieving development. Traditional development approaches such as top-down theory and the bottom-up theory of development have evolved over the years whilst recent approaches such as Randomised Controlled Experiments (RCE) have also emerged with the aim of creating sustainable and more relatable development projects. All these approaches of development have had their fair share of criticism and applauses in literature. The use of Indigenous Knowledge Systems (IK) as a factor of the bottom-up theory of development has been argued as an important element of advancing the developmental agenda and creating sustainable & relatable projects. Many scholars have conducted research around how IK can be incorporated in development projects around the world. Although research has been conducted, much is yet to be discovered around the actual impact or lack thereof of IK as a key factor of the bottom-up theory of development in development projects. This dissertation researched the impact of Rwanda's IK as a factor of the bottom-up theory of development with a focus on Rwanda's Land, Husbandry water harvesting and Hillside irrigation (LWH) project as a unit of analysis. Furthermore, the research assessed whether the Rwandan water harvesting, and irrigation IK played a role in the overall project conceptualization, design and implementation and if so, how this was incorporated in the overall project and finally what role (if any) this IK played in the overall outcomes of the LWH project. A qualitative case study research of the Rwanda's Land Husbandry, Water Harvesting and Irrigation Project was conducted within-depth questionnaires used as data collection instruments from farmers and project coordinators who were immensely involved in the design, development, implementation and monitoring of the project. Data analysis showed that most study participants agreed that the Rwandan water harvesting, and irrigation IK was incorporated in the LWH project and was a key success factor in the bottom-up theory used to implemented in the LWH project. The research found that the incorporation of IK as a factor of the bottom-up theory enabled quicker adoption of the project, increased levels of accountability and responsibility over the project by project beneficiaries and an accelerated attainment of project goals and objectives

Planning horizons and end conditions for sustained yield studies in continuous cover forests

The contemporary forestry preoccupation with non-declining even-flow during yield simulations detracts from more important questions about the constraints that should bind the end of a simulation. Whilst long simulations help to convey a sense of sustainability, they are inferior to stronger indicators such as the optimal state and binding conditions at the end of a simulation. Rigorous definitions of sustainability that constrain the terminal state should allow flexibility in the planning horizon and relaxation of non-declining even-flow, allowing both greater economic efficiency and better environmental outcomes. Suitable definitions cannot be divorced from forest type and management objectives, but should embrace concepts that ensure the anticipated value of the next harvest, the continuity of growing stock, and in the case of uneven-aged management, the adequacy of regeneration.Comment: 8 pages, 1 figure, 54 references, Ecological Indicators (2014

Can forest management based on natural disturbances maintain ecological resilience?

Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance