Embracing thresholds for better environmental management

Three decades of study have revealed dozens of examples in which natural systems have crossed biophysical thresholds (‘tipping points’)—nonlinear changes in ecosystem structure and function—as a result of human-induced stressors, dramatically altering ecosystem function and services. Environmental management that avoids such thresholds could prevent severe social, economic and environmental impacts. Here, we review management measures implemented in ecological systems that have thresholds. Using Ostrom''s social–ecological systems framework, we analysed key biophysical and institutional factors associated with 51 social–ecological systems and associated management regimes, and related these to management success defined by ecological outcomes. We categorized cases as instances of prospective or retrospective management, based upon whether management aimed to avoid a threshold or to restore systems that have crossed a threshold. We find that smaller systems are more amenable to threshold-based management, that routine monitoring is associated with successful avoidance of thresholds and recovery after thresholds have been crossed, and that success is associated with the explicit threshold-based management. These findings are powerful evidence for the policy relevance of information on ecological thresholds across a wide range of ecosystems.     

Chemical mutagens: Dosimetry,Haber's rule and linear systems

We present an overall scheme for chemical mutagen risk assessment, which leads naturally to consideration of Haber's rule, a classical concept of toxicology. A rationale is given for considering compartmental models based on mammalian anatomy and physiology as the most reasonable and practical conceptual framework for risk assessment. Haber's rule is extended to the area of chemical dosimetry, defined in terms of our compartmental models. Then it is proved that Haber's rule holds for any system of linear ordinary differential equations with constant coefficients which is physically realizable. Finally, we comment on non-linearities and on the Blum-Druckey model for time-to-occurrence of tumors.     

Evolution and gradualness

Evolutionary systems are commonly considered to have two fundamental properties: (1) elements (or organisms) in the system reproduce with mutation and (2) only the fit elements survive. I propose that evolutionary systems have a third property — the property of gradualness. A system has gradualness, if, and only if, small changes in an element usually lead to small changes in that element's fitness.I have formalized a framework from which attempts to design evolutionary systems might proceed. Of particular importance are the criteria, based on the notion of perpetuation, which a system's behavior must satisfy in order to be considered evolutionary. By my standards, no computer programs have been designed that manifest meaningful evolutionary behavior.     

Theory and Measurement of the buffer value of bicarbonate in saliva

All known sensory systems have at least two components, which will tend to counteract and compensate for each other. For light, the sensitivity of the eye is some function of the area of the pupil (aperture of the iris diaphragm) and the relative amount of unbleached pigment (visual purple or rhodopsin). An intermittent light will result in a constriction of the pupil and a bleaching of the pigment. The interaction between these two processes results in a total response with components of both a logarithmic and an arithmetic function of the light intensity and duration. The sensitivity of the eye is a linear function of the logarithm of the intensity of incident light (Weber's and Fechner's laws, Fig. 6), yet a rapidly oscillating light causes approximately the same sensitivity as a steady light of the same intensity as the arithmetic average of the fluctuating light (Talbot's and Bloch's laws, Fig. 9c).     

Evaluating Ecosystem Services Provided by Non-Native Species: An Experimental Test in California Grasslands

The concept of ecosystem services – the benefits that nature provides to human''s society – has gained increasing attention over the past decade. Increasing global abiotic and biotic change, including species invasions, is threatening the secure delivery of these ecosystem services. Efficient evaluation methods of ecosystem services are urgently needed to improve our ability to determine management strategies and restoration goals in face of these new emerging ecosystems. Considering a range of multiple ecosystem functions may be a useful way to determine such strategies. We tested this framework experimentally in California grasslands, where large shifts in species composition have occurred since the late 1700''s. We compared a suite of ecosystem functions within one historic native and two non-native species assemblages under different grazing intensities to address how different species assemblages vary in provisioning, regulatory and supporting ecosystem services. Forage production was reduced in one non-native assemblage (medusahead). Cultural ecosystem services, such as native species diversity, were inherently lower in both non-native assemblages, whereas most other services were maintained across grazing intensities. All systems provided similar ecosystem services under the highest grazing intensity treatment, which simulated unsustainable grazing intensity. We suggest that applying a more comprehensive ecosystem framework that considers multiple ecosystem services to evaluate new emerging ecosystems is a valuable tool to determine management goals and how to intervene in a changing ecosystem.     

Precisely incorrect? Monetising the value of ecosystem services

Environmental scientists employ political and economic arguments to argue for the conservation of biodiversity and the maintenance of ecosystem services. However, the economic terminology has a number of connotations which makes its usefulness for the intended effect questionable.On the one hand, the basic assumptions underlying economic valuation are far from realistic and represent rather a caricature of human behaviour. On the other hand, the methods based on these assumptions are manifold and lead to wildly diverging results. Thus the calculated value of ecosystems and their services is not a robust figure, but varies with the valuation method applied (plus a plethora of subjective assumptions). As a result, it is not possible to ‘objectively’ calculate the value of ecosystem services. Fortunately, it is also not necessary to do so. Given the inherent flaws of the valuation process, it seems more promising for biodiversity and its conservation to restrict the economic calculus to the role of a contribution in the implementation process for a set of politically defined targets, rather than using it as the target setting mechanism itself.The paper lists some of the core assumptions, presents a systematic overview of the most relevant valuation methods, illustrates them by providing examples and discusses their limitations. As an alternative, political target setting is suggested, based on a multi-stakeholder, multi-criteria analysis. Market prices play a role in this analysis, as one factor amongst others. For the implementation, cost-effectiveness analysis gives important hints, and economic instruments – inter alia – can play an important role as enforcement mechanisms. However, incentives should be based on criteria of (potential) effectiveness, not on value calculations.     

Economic and ecological views on climate change mitigation with bioenergy and negative emissions

Climate stabilization scenarios emphasize the importance of land‐based mitigation to achieve ambitious mitigation goals. The stabilization scenarios informing the recent IPCC's Fifth Assessment Report suggest that bioenergy could contribute anywhere between 10 and 245 EJ to climate change mitigation in 2100. High deployment of bioenergy with low life cycle GHG emissions would enable ambitious climate stabilization futures and reduce demands on other sectors and options. Bioenergy with carbon capture and storage (BECCS) would even enable so‐called negative emissions, possibly in the order of magnitude of 50% of today's annual gross emissions. Here, I discuss key assumptions that differ between economic and ecological perspectives. I find that high future yield assumptions, plausible in stabilization scenarios, look less realistic when evaluated in biophysical metrics. Yield assumptions also determine the magnitude of counterfactual land carbon stock development and partially determine the potential of BECCS. High fertilizer input required for high yields would likely hasten ecosystem degradation. I conclude that land‐based mitigation strategies remain highly speculative; a constant iteration between synoptic integrated assessment models and more particularistic and fine‐grained approaches is a crucial precondition for capturing complex dynamics and biophysical constraints that are essential for comprehensive assessments.     

Trading Off Global Fuel Supply,CO2 Emissions and Sustainable Development

The United Nations Conference on Climate Change (Paris 2015) reached an international agreement to keep the rise in global average temperature ‘well below 2°C’ and to ‘aim to limit the increase to 1.5°C’. These reductions will have to be made in the face of rising global energy demand. Here a thoroughly validated dynamic econometric model (Eq 1) is used to forecast global energy demand growth (International Energy Agency and BP), which is driven by an increase of the global population (UN), energy use per person and real GDP (World Bank and Maddison). Even relatively conservative assumptions put a severe upward pressure on forecast global energy demand and highlight three areas of concern. First, is the potential for an exponential increase of fossil fuel consumption, if renewable energy systems are not rapidly scaled up. Second, implementation of internationally mandated CO₂ emission controls are forecast to place serious constraints on fossil fuel use from ~2030 onward, raising energy security implications. Third is the challenge of maintaining the international ‘pro-growth’ strategy being used to meet poverty alleviation targets, while reducing CO₂ emissions. Our findings place global economists and environmentalists on the same side as they indicate that the scale up of CO₂ neutral renewable energy systems is not only important to protect against climate change, but to enhance global energy security by reducing our dependence of fossil fuels and to provide a sustainable basis for economic development and poverty alleviation. Very hard choices will have to be made to achieve ‘sustainable development’ goals.     

Global Scenarios: Background Review for the Millennium Ecosystem Assessment

The long-range outlook for the world’s ecosystems depends on the course taken by global development in the coming decades. Current global trends and ecological dynamics are consistent with very different outcomes, defined by alternative assumptions about the technological, economic, demographic, geopolitical, and social aspects of development and the ways in which institutions, personal and public values, and natural systems may be expected to respond to historically novel stressors. Recent advances in scenario analysis have addressed the dual methodological challenge of exploring these uncertainties in an organized way and determining what would be needed to make the transition to sustainability. This paper reviews global scenario research, setting current efforts in a historical context. It focuses on seven recent studies that are comprehensive, regionally disaggregated, and narratively rich—and thus of greatest relevance to the Millennium Ecosystem Assessment (MA). It summarizes their social visions and the level of quantitative detail used in these exercises. Taken together, this suite of global scenario studies provides a useful platform for the MA by offering insight into the complex factors that drive ecosystem change, estimating the magnitude of regional pressures on ecosystems, sounding the alert on critical uncertainties that could undermine sustainable development, and understanding the importance of institutions and values. But these studies are only a point of departure. The integration of changing ecosystem conditions into global development scenarios, as both effects and causes, is at the cutting edge of scenario analysis. The paper concludes by identifying directions for this research program and suggesting ways that the MA can contribute to this effort.     

Scenario Analysis and Path Selection of Low-Carbon Transformation in China Based on a Modified IPAT Model

This paper presents a forecast and analysis of population, economic development, energy consumption and CO₂ emissions variation in China in the short- and long-term steps before 2020 with 2007 as the base year. The widely applied IPAT model, which is the basis for calculations, projections, and scenarios of greenhouse gases (GHGs) reformulated as the Kaya equation, is extended to analyze and predict the relations between human activities and the environment. Four scenarios of CO₂ emissions are used including business as usual (BAU), energy efficiency improvement scenario (EEI), low carbon scenario (LC) and enhanced low carbon scenario (ELC). The results show that carbon intensity will be reduced by 40–45% as scheduled and economic growth rate will be 6% in China under LC scenario by 2020. The LC scenario, as the most appropriate and the most feasible scheme for China’s low-carbon development in the future, can maximize the harmonious development of economy, society, energy and environmental systems. Assuming China''s development follows the LC scenario, the paper further gives four paths of low-carbon transformation in China: technological innovation, industrial structure optimization, energy structure optimization and policy guidance.     

70年来陕西省纸坊沟流域农业生态经济系统耦合态势

"农业生态经济系统耦合"的研究与实践对于实现农业产业与资源相一致,建立持续、高效的农业生态经济系统具有重要的意义.耦合度可以阐明农业经济系统与农业生态系统互动关系,判定农业生态经济系统耦合态势.在分析陕西省纸坊沟流域农业生态经济系统耦合关系的基础上,参照系统科学等理论及相关研究结果建立了农业经济系统与农业生态系统耦合度模型,并计算和分析了该流域70a来的耦合度.结果表明,农业生态经济系统的耦合过程可以划分为4个阶段:Ⅰ.经济系统依赖生态资源进行原始化农业生产阶段;Ⅱ.农业生产掠夺式利用生态资源,生态系统供给能力不断减少阶段;Ⅲ. 农业经济系统与生态系统协调化发展阶段;Ⅳ.降低农业发展速度,促使生态系统重建阶段.纸坊沟流域从1938～2008年先后经历了第Ⅰ阶段、第Ⅱ阶段和第Ⅲ阶段.目前处于第Ⅲ阶段,但在"系统发展"过程中已潜伏了越来越大的危机,到2018年系统耦合突破"协调"界限,"相悖态势"将明显表现出来.为此,纸坊沟流域必须调整产业布局,发展草畜产业,进行产业升级,优化产业结构,实现农业生态经济系统协调、持续发展.     

Ecosystem stability: a result from an abstract simulation

An abstract model of an ecosystem is presented which incorporates both population dynamic and energy flow concepts and attempts to avoid the simple assumptions of the Lotka-Volterra or mass-action types of equation. The model allows simulation of very complex foodwebs, involving all trophic levels, with 50 or more species.The results indicate unusual stability features for such models; for systems with a range of species numbers, multiple stable points (or limits cycles) are found in which all species survive. Various views of the relationship between stability and species diversity are reconciled by the following conclusion of the study. “With increasing species numbers in an ecosystem similar to that described here, there is an increase in stable points due to compensating adjustments with increasing food web complexity, however stability declines, in the sense that the equilibrium points become less aggregated in the vector field.”     

Separating Macroecological Pattern and Process: Comparing Ecological,Economic, and Geological Systems

Theories of biodiversity rest on several macroecological patterns describing the relationship between species abundance and diversity. A central problem is that all theories make similar predictions for these patterns despite disparate assumptions. A troubling implication is that these patterns may not reflect anything unique about organizational principles of biology or the functioning of ecological systems. To test this, we analyze five datasets from ecological, economic, and geological systems that describe the distribution of objects across categories in the United States. At the level of functional form (‘first-order effects’), these patterns are not unique to ecological systems, indicating they may reveal little about biological process. However, we show that mechanism can be better revealed in the scale-dependency of first-order patterns (‘second-order effects’). These results provide a roadmap for biodiversity theory to move beyond traditional patterns, and also suggest ways in which macroecological theory can constrain the dynamics of economic systems.     

陇中黄土丘陵区土地利用强度-生态系统服务-人类福祉时空关系研究——以安定区为例

基于土地利用和社会统计数据,构建了"土地利用强度-生态系统服务-人类福祉"多尺度分析框架,从县区和乡镇尺度探讨了定西市安定区1990—2015年土地利用强度-生态系统服务-人类福祉的时空权衡/协同关系。结果表明:1990—2015年安定区土地利用强度-生态系统服务-人类福祉关系变化存在区域整体相似性和乡镇局部差异性;土地利用强度的增加,提高了供给服务和生产资料供给福祉,但弱化了调节和支持服务;供给与支持服务权衡主要集中于安定区北部和西南部。该区生态系统服务间的权衡程度较高,不利于生态系统服务保育和居民福祉的持续提升。区域的脱贫致富因立足于提高居民福祉,退耕还林还草、发展特色高效产业、劳务输出等是实现该区社会生态系统的经济收益与生态效益共赢的有效途径。     

Quantifying drylands' drought resistance and recovery: the importance of drought intensity,dominant life history and grazing regime

Projected global change will increase the level of land‐use and environmental stressors such as drought and grazing, particularly in drylands. Still, combined effects of drought and grazing on plant production are poorly understood, thus hampering adequate projections and development of mitigation strategies. We used a large, cross‐continental database consisting of 174 long‐term datasets from >30 dryland regions to quantify ecosystem responses to drought and grazing with the ultimate goal to increase functional understanding in these responses. Two key aspects of ecosystem stability, resistance to and recovery after a drought, were evaluated based on standardized and normalized aboveground net primary production (ANPP) data. Drought intensity was quantified using the standardized precipitation index. We tested effects of drought intensity, grazing regime (grazed, ungrazed), biome (grassland, shrubland, savanna) or dominant life history (annual, perennial) of the herbaceous layer to assess the relative importance of these factors for ecosystem stability, and to identify predictable relationships between drought intensity and ecosystem resistance and recovery. We found that both components of ecosystem stability were better explained by dominant herbaceous life history than by biome. Increasing drought intensity (quasi‐) linearly reduced ecosystem resistance. Even though annual and perennial systems showed the same response rate to increasing drought intensity, they differed in their general magnitude of resistance, with annual systems being ca. 27% less resistant. In contrast, systems with an herbaceous layer dominated by annuals had substantially higher postdrought recovery, particularly when grazed. Combined effects of drought and grazing were not merely additive but modulated by dominant life history of the herbaceous layer. To the best of our knowledge, our study established the first predictive, cross‐continental model between drought intensity and drought‐related relative losses in ANPP, and suggests that systems with an herbaceous layer dominated by annuals are more prone to ecosystem degradation under future global change regimes.     

Female courtship summation in Drosophila melanogaster

To examine the concept of female courtship summation in Drosophila melanogaster, two experiments previously reported in the literature, the first involving repeated matings of females and the second progressive removal of the males' wings, were repeated. The present results do not convincingly support the concept of female summation of stimuli provided by the males' courtship. The results of the first experiment also refute the idea that low male courtship intensity leads to long courtships. These results also fail to support an earlier suggestion that females summate the sine rather than pulse song component of the males' wing vibration. Instead, the variation in courtship duration appeared to result from the inverse hyperbolic relationship between the male latency to courtship and the subsequent courtship duration. Thus short male latencies led to longer courtship durations. This is interpreted as resulting from a female latency period during which the female is too agitated to receive the male's courtship, and after which she mates upon recognizing the male as conspecific. In addition, very long courtships largely resulted from additional agitation of the female by the male's courtship. Long courtships therefore appear to be an artifact of the experimental situation and the established concept of female courtship summation, which is supposed to explain them, is unnecessary. The implications of this conclusion are discussed.     

雄安新区生态系统服务需求空间分布格局预测

设立雄安新区是千年大计、国家大事。明晰生态系统服务需求的空间分布及时间变化趋势,有助于探究雄安新区生态系统服务对社会经济发展的促进和制约作用,支持生态系统服务管理和政策的执行。在已有对单一时间维度的生态系统服务研究基础上,增加了对时空变异性的关注,对雄安新区未来时间节点生态系统服务需求的时空分布特征进行预测,首先选取土地利用开发程度、人口密度、经济密度3个指标建立了生态系统服务需求预测模型,然后根据综合增长率法和地区类比法预测土地利用格局、人口密度和经济密度,最后叠加分析得到雄安新区2035年和2050年生态系统服务需求空间分布格局。预测结果表明,2035年起步区人口密度和经济密度将大幅增加,进而带动生态系统服务需求的增加;本世纪中叶,新区人口密度和经济密度的绝对值将大幅度提高,生态系统服务需求高值区主要集中在"一主、五辅"城区范围,与城乡空间布局相呼应。基于研究结果,提出优化土地利用结构、加强白洋淀保护与修复和建设宏观-中观-微观多尺度生态基础设施几条建议,以期为未来的生态系统服务供给、生态基础设施建设和城市规划布局等提供指导。     

Predation and the evolution of gregariousness. II. An economic model for predator-prey interaction

An earlier paper presented models which allow the relative advantages of different prey dispersions to be assessed for two cases: when the prey's main defence is concealment, and when prey may evade the predator (Treisman 1975). With these as a basis, an economic model for predator-prey interaction is developed which takes explicit account of the conflicts between the need to maintain watch for a predator and the prey's other needs. The model embodies arguments based on statistical decision theory which allow factors such as the degree of predation threat, the watchfulness of the prey and the number of watchers to be related to the expected value of the prey's performance. The model provides a basis for predicting the optimal number of watchers or optimal group size under various conditions. The advantages of different group configurations are compared, and it is shown that animals which aggregate (and maintain a high sensory decision criterion) will have an advantage over solitary animals under certain conditions.