Tamara Hochstrasser

Climate change-induced vegetation shifts lead to more ecological droughts despite projected rainfall increases in many global temperate drylands

Drylands occur worldwide and are particularly vulnerable to climate change because dryland ecosystems depend directly on soil water availability that may become increasingly limited as temperatures rise. Climate change will both directly impact soil water availability and change plant biomass, with resulting indirect feedbacks on soil moisture. Thus, the net impact of direct and indirect climate change effects on soil moisture requires better understanding. We used the ecohydrological simulation model SOILWAT at sites from temperate dryland ecosystems around the globe to disentangle the contributions of direct climate change effects and of additional indirect, climate change-induced changes in vegetation on soil water availability. We simulated current and future climate conditions projected by 16 GCMs under RCP 4.5 and RCP 8.5 for the end of the century. We determined shifts in water availability due to climate change alone and due to combined changes of climate and the growth form and biomass of vegetation. Vegetation change will mostly exacerbate low soil water availability in regions already expected to suffer from negative direct impacts of climate change (with the two RCP scenarios giving us qualitatively similar effects). By contrast, in regions that will likely experience increased water availability due to climate change alone, vegetation changes will counteract these increases due to increased water losses by interception. In only a small minority of locations, climate change-induced vegetation changes may lead to a net increase in water availability. These results suggest that changes in vegetation in response to climate change may exacerbate drought conditions and may dampen the effects of increased precipitation, that is, leading to more ecological droughts despite higher precipitation in some regions. Our results underscore the value of considering indirect effects of climate change on vegetation when assessing future soil moisture conditions in water-limited ecosystems.

Current practice in biodiversity impact assessment and prospects for developing an integrated process

Irish guidance for Integrated Biodiversity Impact Assessment provides a methodological approach for integrating impact assessment requirements, with regard to biodiversity, under EU and Irish legislation. Preparation of the guidance was supported by extensive consultation, including international and national surveys. These offered insights into the issues affecting the treatment of biodiversity in impact assessment practice as well as expert opinion on factors affecting and supporting the development of a more integrated and adaptive approach. This paper contrasts the international literature with the consultation feedback. Among other aspects, the results highlight the requirement for an improved application of evidence-based assessment techniques, continuity in monitoring, enhanced information exchange between scientists, assessors and proponents, as well as increased awareness amongst stakeholders for inclusion of appropriate biodiversity protection objectives and mitigation in final planning decisions. Comparative analysis of results indicates that current practice is characterized by limited information exchange and the use of in-house databases in assessments. A central spatial data repository is identified as key for quantitatively assessing (cumulative) effects through Geographic Information Systems, and thus supporting evidence-informed decision-making towards biodiversity conservation.

The Study of Land Degradation in Drylands: State of the Art

Land degradation is difficult to define because land can only be considered degraded with respect to some use to which it may be put. However, physical and biological properties of the landscape are typically measured to characterize degradation rather than its inherent or potential utility. One approach to characterizing land degradation is by assessing the provisioning of ecosystem services. Most provisioning ecosystem services depend on water, and water management is crucial to maintaining and increasing ecosystem services in arid lands. In contrast, vegetation change has been most commonly employed as an indicator of land degradation. Nevertheless, the close relationship that exists between vegetation and other biophysical processes of the environment means that any change in vegetation will result in a concomitant change to these other processes also. Of particular importance is a change in vegetation distribution since the spatial distribution of associated biophysical parameters controls landscape fluxes, and hence degradation, by controlling landscape connectivity. From a management perspective, an understanding of the degree of connectivity in a landscape can aid in triage of remediation efforts. Areas that are dominated by long connected pathways will not respond to localized, small-scale manipulations because those pathways present inertia that a small-scale manipulation cannot overcome. Two important ecosystem services provided by drylands are grazing land and agricultural land. Both land uses can be drivers of degradation. The role of grazing in land degradation depends on several factors which can be grouped into three categories: number of animals, kind of animal species and grazing system. For agriculture, systematic crop residue removal without fertilisation, poor cultivation practices and extensive soil salinization are examples of mismanagement that may lead to land degradation. Aside from the immediate provisioning of food, drylands provide ecosystem services at a broader scale. Drylands are highly significant to the global carbon cycle. Land degradation in drylands has implications for the effectiveness of carbon sequestration as well as for storage (through soil erosion). Because many dryland soils have been degraded they are currently far from saturated with carbon and as a result their potential to sequester carbon may be highly significant. To understand land degradation better, efforts have been made to develop integrated human-environment research that overcomes the perceived deficiencies of reductionist, discipline-based research. However, much integrated environmental research to-date has resulted in a ‘hierarchical relationship’ between the human and physical components. Three approaches have been advocated to improve human-environment understanding: (a) systems science that emphasises feedbacks between integrated human and natural systems; (b) computer-simulation modelling that explicitly represents the interaction of individual human decisions and physical processes; and (c) participatory research that emphasises engagement with the actors in the region being studied. However, many questions remain open, and advancing beyond narrow scientific disciplinary specialization is vital if the hierarchical relationship in understanding physical and social causes of land degradation is to be broken.

Approaches to Modelling Ecogeomorphic Systems

Drivers of land degradation often co-occur and their effects are often non-additive because of internal system feedbacks. Therefore, to understand how drivers of land degradation alter ecogeomorphic patterns and processes, novel tools are required. In this chapter we explore different modelling approaches that have been developed to simulate pattern formation, and ecological and geomorphic processes. These modelling approaches reflect some of the best available tools at present, but notably, they tend to simulate only one or at best two components of the ecogeomorphic system. The chapter culminates with a discussion of these different modelling approaches and how they provide a foundation upon which to develop much needed ecogeomorphic modelling tools.

Evaluating Ireland's IBIA as an approach to improving the quality and effectiveness of biodiversity impact assessment

The assessment of potential impacts of plans, programmes and projects on biodiversity is required under various legislative remits (including the European Unions Habitats, Strategic Environmental Assessment and Environmental Impact Assessment Directives). The objective of such assessments is to ensure that potential negative impacts on both protected nature conservation sites and species and wider biodiversity are efficiently identified in a timely manner, quantified and subsequently avoided or mitigated, while enhancing positive effects. The procedural requirements of these legal obligations vary and, as a result, differing methodological steps, data gathering and analysis methods, and impact assessment techniques are commonly applied under each individual process, often leading to uncoordinated assessment efforts and results (in terms, for example, of scope, scale and assessment detail). In order to address these issues and improve current practice, an Integrated Biodiversity Impact Assessment (IBIA) methodology has been developed in Ireland with the overall aim of providing a holistic and systematic approach to biodiversity impact assessment. The IBIA framework seeks to ensure that relevant procedures are effectively integrated, time and resource efficiencies are optimised, and unnecessary duplication avoided. Particular emphasis is given to compliance with legal requirements, integration and communication of scientific knowledge, spatial assessment and biodiversity data considerations, and integration of biodiversity aspects with a variety of other concerns during the plan-making process. This paper presents the IBIA methodology and critically examines current key issues in biodiversity impact assessment that can be potentially addressed through IBIA, as well as remaining challenges. In addition, and in order to support the examination of the anticipated benefits of using this new methodological framework (such as biodiversity-inclusive planning through improved communication and coordinated assessment), two contrasting case studies are used, one pre-dating the development of IBIA and a second where elements of IBIA have been implemented.

The study of land degradation in drylands

Land degradation is difficult to define because land can only be considered degraded with respect to some use to which it may be put. However, physical and biological properties of the landscape are typically measured to characterize degradation rather than its inherent or potential utility. One approach to characterizing land degradation is by assessing the provisioning of ecosystem services. Most provisioning ecosystem services depend on water, and water management is crucial to maintaining and increasing ecosystem services in arid lands. In contrast, vegetation change has been most commonly employed as an indicator of land degradation. Nevertheless, the close relationship that exists between vegetation and other biophysical processes of the environment means that any change in vegetation will result in a concomitant change to these other processes also. Of particular importance is a change in vegetation distribution since the spatial distribution of associated biophysical parameters controls landscape fluxes, and hence degradation, by controlling landscape connectivity. From a management perspective, an understanding of the degree of connectivity in a landscape can aid in triage of remediation efforts. Areas that are dominated by long connected pathways will not respond to localized, small-scale manipulations because those pathways present inertia that a small-scale manipulation cannot overcome. Two important ecosystem services provided by drylands are grazing land and agricultural land. Both land uses can be drivers of degradation. The role of grazing in land degradation depends on several factors which can be grouped into three categories: number of animals, kind of animal species and grazing system. For agriculture, systematic crop residue removal without fertilisation, poor cultivation practices and extensive soil salinization are examples of mismanagement that may lead to land degradation. Aside from the immediate provisioning of food, drylands provide ecosystem services at a broader scale. Drylands are highly significant to the global carbon cycle. Land degradation in drylands has implications for the effectiveness of carbon sequestration as well as for storage (through soil erosion). Because many dryland soils have been degraded they are currently far from saturated with carbon and as a result their potential to sequester carbon may be highly significant. To understand land degradation better, efforts have been made to develop integrated human-environment research that overcomes the perceived deficiencies of reductionist, discipline-based research. However, much integrated environmental research to-date has resulted in a ‘hierarchical relationship’ between the human and physical components. Three approaches have been advocated to improve human-environment understanding: (a) systems science that emphasises feedbacks between integrated human and natural systems; (b) computer-simulation modelling that explicitly represents the interaction of individual human decisions and physical processes; and (c) participatory research that emphasises engagement with the actors in the region being studied. However, many questions remain open, and advancing beyond narrow scientific disciplinary specialization is vital if the hierarchical relationship in understanding physical and social causes of land degradation is to be broken.

Complexity Should not be Construed as Confusion

One might be tempted to grant to Sagoff the homely adage that values come from the heart, not the head; and, moreover, be tempted to grant to him the naive simplification that science is a value-free activity of the head. Sagoff, then, would have no work to do to convince one that ‘ecological theory can neither explain which aspects of the natural world we should count as “environmental” nor tell us why we should care about them . . . ’ (Sagoff, 2013). However, Sagoff’s argument isn’t just new lipstick on the time-worn ‘fact/ value dichotomy’ pig. That ecology has ‘failed’ to guide a re-conceptualization of ‘the environment’—failed to deliver to the US EPA the ‘Holy Grail’ of ‘regulatory endpoints’, and fails to inspire the environmentalist’s sentiments—is traced by Sagoff to a problem with the science itself: the vocabulary in which the ecological theorist conducts her business is meaningless. No one—not environmentalists, not policy makers, not scientists themselves—understands it. This is quite a strong claim. And one might consider taking it seriously if what Sagoff seems to mean by ‘meaningless’ didn’t so plainly apply to his own alternative to ecological theory. What does environmental protection protect? According to Sagoff, today’s environmentalists are facing a crisis. The kind of concerns that defined their raison d’être—exemplified by flaming rivers and smog-choked city air—apparently is a thing of the past; in our post-public-health-emergency world, the activist needs to supplement her conception of ‘the environment’. Sagoff sees this task as beginning with a clear definition of what it is the environmentalist means to be protecting. But are there really no more public-health challenges for the environmentalist? If the river in Cleveland no longer catches fire, are worries about the effects of fracking or groundwater depletion negligible? Are Gulf of Mexico oil spills only ‘mopping-up operations’? And even if it’s the case—within the cozy boundaries of the USA—that the fly-fishing is great, is it of no concern to the environmentalist that Beijing’s air is often poisonous, that deforestation may again be on the rise in Brazil, that global fish stocks are plummeting? (And this is saying nothing of the various predicted manifestations of ‘climate change’. The vast sweep of this latter concept may be daunting, as Sagoff fears; but its effects will be felt by real people in the real places they ‘visit’ or live in.) If it’s a lack of back-yard troubles that motivates Sagoff’s environmental ennui, then he should take a look over his fence.