Agricultural modifications of hydrological flows create ecological surprises

Forecasting the effects of land use scenarios on farmland birds reveal a potential mitigation of climate change impacts

Climate and land use changes are key drivers of current biodiversity trends, but interactions between these drivers are poorly modeled, even though they could amplify or mitigate negative impacts of climate change. Here, we attempt to predict the impacts of different agricultural change scenarios on common breeding birds within farmland included in the potential future climatic suitable areas for these species. We used the Special Report on Emissions Scenarios (SRES) to integrate likely changes in species climatic suitability, based on species distribution models, and changes in area of farmland, based on the IMAGE model, inside future climatic suitable areas. We also developed six farmland cover scenarios, based on expert opinion, which cover a wide spectrum of potential changes in livestock farming and cropping patterns by 2050. We ran generalized linear mixed models to calibrate the effects of farmland cover and climate change on bird specific abundance within 386 small agricultural regions. We used model outputs to predict potential changes in bird populations on the basis of predicted changes in regional farmland cover, in area of farmland and in species climatic suitability. We then examined the species sensitivity according to their habitat requirements. A scenario based on extensification of agricultural systems (i.e., low-intensity agriculture) showed the greatest potential to reduce reverse current declines in breeding birds. To meet ecological requirements of a larger number of species, agricultural policies accounting for regional disparities and landscape structure appear more efficient than global policies uniformly implemented at national scale. Interestingly, we also found evidence that farmland cover changes can mitigate the negative effect of climate change. Here, we confirm that there is a potential for countering negative effects of climate change by adaptive management of landscape. We argue that such studies will help inform sustainable agricultural policies for the future.

Marine regime shifts: drivers and impacts on ecosystems services

Marine ecosystems can experience regime shifts, in which they shift from being organized around one set of mutually reinforcing structures and processes to another. Anthropogenic global change has broadly increased a wide variety of processes that can drive regime shifts. To assess the vulnerability of marine ecosystems to such shifts and their potential consequences, we reviewed the scientific literature for 13 types of marine regime shifts and used networks to conduct an analysis of co-occurrence of drivers and ecosystem service impacts. We found that regime shifts are caused by multiple drivers and have multiple consequences that co-occur in a non-random pattern. Drivers related to food production, climate change and coastal development are the most common co-occurring causes of regime shifts, while cultural services, biodiversity and primary production are the most common cluster of ecosystem services affected. These clusters prioritize sets of drivers for management and highlight the need for coordinated actions across multiple drivers and scales to reduce the risk of marine regime shifts. Managerial strategies are likely to fail if they only address well-understood or data-rich variables, and international cooperation and polycentric institutions will be critical to implement and coordinate action across the scales at which different drivers operate. By better understanding these underlying patterns, we hope to inform the development of managerial strategies to reduce the risk of high-impact marine regime shifts, especially for areas of the world where data are not available or monitoring programmes are not in place.

Long-term agroecosystem research in the central Mississippi river basin: goodwater creek experimental watershed flow data

Flow monitoring in Goodwater Creek Experimental Watershed started in 1971 at three nested watersheds ranging from 12 to 73 km. Since then, runoff or stream flow has been measured at 14 plots, three fields, and 12 additional stream sites ranging from 0.0034 to 6067 km in the Central Mississippi River Basin. Long-term data sets are important to document the changes resulting from anthropogenic and natural drivers. The data set presented here documents discharge across a range of catchment sizes in an area known for its high runoff potential. It constitutes the flow database of the Central Mississippi River Basin site of the Long-Term Agricultural Research network. Like the other sites of this network, data are accessible through the STEWARDS web interface (). Here we (i) describe the data collection methods, (ii) document the data available at plot, field, and watershed scales, and (iii) provide the main characteristics of discharge. General characteristics of discharge per unit area for different cropping system management systems show that in this claypan soil setting, management and tillage of row crop systems do not affect surface flow during the growing season (April-October). Data from fields and stream sites show the dampening of peak flow values and lengthening of storm hydrographs caused by mixed land uses and longer times of concentration. Overall, stream flow accounts for a third of the precipitation, of which 80% is from surface runoff and 20% is from groundwater.

Long-lived organisms provide an integrative footprint of agricultural land use

Nitrogen (N) fertilizer runoff into rivers is linked to nutrient enrichment, hydrologic alteration, habitat degradation and loss, and declines in biotic integrity in streams. Nitrogen runoff from agriculture is expected to increase with population growth, so tracking these sources is vital to enhancing biomonitoring and management actions. Unionid mussels are large, long-lived, sedentary, primary consumers that transfer particulate material and nutrients from the water column to the sediments through their filter feeding. Because of these traits, mussels may provide a temporal integration of nitrogen inputs into watersheds. Our goals were to (1) establish a baseline delta15N signature for unionid mussels in watersheds not heavily influenced by agriculture for use in comparative analyses and (2) determine if mussels provide an integrative measure of N sources in watersheds with varying percentages of agriculture across large spatial scales. We compiled tissue delta15N data for 20 species of mussels from seven geographic areas, including 23 watersheds and 42 sample sites that spanned varying degrees of agricultural intensification across the eastern United States and Canada. We used GIS to determine land cover within the study basins, and we estimated net anthropogenic nitrogen inputs (NANI) entering these systems. We then determined the relationship between mussel tissue delta15N and percentage of land in agriculture (%AG) and net anthropogenic N loading. The delta15N of mussel tissue could be predicted from both %AG and net anthropogenic N loading, and one component of NANI, the amount of N fertilizer applied, was strongly related to the delta15N of mussel tissue. Based on our results, mussels occupying a system not affected by agricultural land use would have a baseline delta15N signature of approximately 2.0 pe thousand, whereas mussels in basins with heavy agriculture had delta15N signatures of 13.6 per thousand. Our results demonstrate that mussels integrate anthropogenic N input into rivers at a watershed scale and could be a good bioassessment tool for tracking agriculture N sources.

Rates of disturbance vary by data resolution: implications for conservation schedules using the Alberta boreal forest as a case study

Investigations of biophysical changes on earth caused by anthropogenic disturbance provide governments with tools to generate sustainable development policy. Canada currently experiences one of the fastest rates of boreal forest disturbance in the world. Plans to conserve the 330 000 km(2) boreal forest in the province of Alberta exist but conservation targets and schedules must be aligned with rates of forest disturbance. We explore how disturbance rate, and the accuracy with which we detect it, may affect conservation success. We performed a change detection analysis from 1992 to 2008 using Landsat and SPOT satellite image data processing. Canada's recovery strategy for boreal caribou (Rangifer tarandus caribou) states that ≤35% of a caribou range can be either burned or within 500 m of a man-made feature for caribou to recover. Our analyses show that by 2008 78% of the boreal forest was disturbed and that, if the current rate continues, 100% would be disturbed by 2028. Alberta plans to set aside 22% for conservation in a region encompassing oil sands development to balance economic, environmental, and traditional indigenous land-use goals. Contrary to the federal caribou recovery strategy, provincial conservation plans do not consider wildfire a disturbance. Based on analyses used in the provincial plan, we apply a 250 m buffer around anthropogenic footprints. Landsat image analysis indicates that the yearly addition of disturbance is 714 km(2) (0.8%). The higher resolution SPOT images show fine-scale disturbance indicating that actual disturbance was 1.28 times greater than detected by Landsat. If the SPOT image based disturbance rates continue, the 22% threshold may be exceeded within the next decade, up to 20 years earlier than indicated by Landsat-based analysis. Our results show that policies for sustainable development will likely fail if governments do not develop time frames that are grounded by accurate calculations of disturbance rates.

Phosphorus mitigation to control river eutrophication: murky waters, inconvenient truths, and "postnormal" science

This commentary examines an "inconvenient truth" that phosphorus (P)-based nutrient mitigation, long regarded as the key tool in eutrophication management, in many cases has not yet yielded the desired reductions in water quality and nuisance algal growth in rivers and their associated downstream ecosystems. We examine why the water quality and aquatic ecology have not recovered, in some case after two decades or more of reduced P inputs, including (i) legacies of past land-use management, (ii) decoupling of algal growth responses to river P loading in eutrophically impaired rivers; and (iii) recovery trajectories, which may be nonlinear and characterized by thresholds and alternative stable states. It is possible that baselines have shifted and that some disturbed river environments may never return to predisturbance conditions or may require P reductions below those that originally triggered ecological degradation. We discuss the practical implications of setting P-based nutrient criteria to protect and improve river water quality and ecology, drawing on a case study from the Red River Basin in the United States. We conclude that the challenges facing nutrient management and eutrophication control bear the hallmarks of "postnormal" science, where uncertainties are large, management intervention is urgently required, and decision stakes are high. We argue a case for a more holistic approach to eutrophication management that includes more sophisticated regime-based nutrient criteria and considers other nutrient and pollutant controls and river restoration (e.g., physical habitat and functional food web interactions) to promote more resilient water quality and ecosystem functioning along the land-freshwater continuum.

Effects of hydromorphology and riparian vegetation on the sediment quality of agricultural low-order streams: consequences for stream restoration

Intensive agricultural land use imposes multiple pressures on streams. More specifically, the loading of streams with nutrient-enriched soil from surrounding crop fields may deteriorate the sediment quality. The current study aimed to find out whether stream restoration may be an effective tool to improve the sediment quality of agricultural headwater streams. We compared nine stream reaches representing different morphological types (forested meandering reaches vs. deforested channelized reaches) regarding sediment structure, sedimentary nutrient and organic matter concentrations, and benthic microbial respiration. Main differences among reach types were found in grain sizes. Meandering reaches featured larger mean grain sizes (50-70 μm) and a thicker oxygenated surface layer (8 cm) than channelized reaches (40 μm, 5 cm). Total phosphorous amounted for up to 1,500 μg g(-1) DW at retentive channelized reaches and 850-1,050 μg g(-1) DW at the others. While N-NH(4) accumulated in the sediments (60-180 μg g(-1) DW), N-NO(3) concentrations were generally low (2-5 μg g(-1) DW). Benthic respiration was high at all sites (10-20 g O(2) m(-2) day(-1)). Our study shows that both hydromorphology and bank vegetation may influence the sediment quality of agricultural streams, though effects are often small and spatially restricted. To increase the efficiency of stream restoration in agricultural landscapes, nutrient and sediment delivery to stream channels need to be minimized by mitigating soil erosion in the catchment.

Reconnecting to the biosphere

Humanity has emerged as a major force in the operation of the biosphere, with a significant imprint on the Earth System, challenging social-ecological resilience. This new situation calls for a fundamental shift in perspectives, world views, and institutions. Human development and progress must be reconnected to the capacity of the biosphere and essential ecosystem services to be sustained. Governance challenges include a highly interconnected and faster world, cascading social-ecological interactions and planetary boundaries that create vulnerabilities but also opportunities for social-ecological change and transformation. Tipping points and thresholds highlight the importance of understanding and managing resilience. New modes of flexible governance are emerging. A central challenge is to reconnect these efforts to the changing preconditions for societal development as active stewards of the Earth System. We suggest that the Millennium Development Goals need to be reframed in such a planetary stewardship context combined with a call for a new social contract on global sustainability. The ongoing mind shift in human relations with Earth and its boundaries provides exciting opportunities for societal development in collaboration with the biosphere--a global sustainability agenda for humanity.

Coastal marine eutrophication assessment: a review on data analysis

A wide variety of data analysis techniques have been applied for quantitative assessment of coastal marine eutrophication. Indicators for assessing eutrophication and frequency distributions have been used to develop scales for characterizing oligotrophy and eutrophication. Numerical classification has also contributed to the assessment of eutrophic trends by grouping sampling sites of similar trophic conditions. Applications of eutrophication assessment based on Principal Component Analysis and Multidimensional Scaling have also been carried out. In addition, the rapid development of Geographical Information Systems has provided the framework for applications of spatial methods and mapping techniques on eutrophication studies. Satellite data have also contributed to eutrophication assessment especially at large scale. Multiple criteria analysis methods can integrate eutrophication variables together with socio-economic parameters providing a holistic approach particularly useful to policy makers. As the current concept of eutrophication problems is to be examined as part of a coastal management approach, more complex quantitative procedures are needed to provide a platform useful for implementation of environmental policy. The present work reviews methods of data analysis used for the assessment of coastal marine eutrophication. The difficulties in applying these methods on data collected from the marine environment are discussed as well as the future perspectives of spatial and multiple criteria choice methods.

Improved probability of detection of ecological "surprises"

Ecological "surprises" are defined as unexpected findings about the natural environment. They are critically important in ecology because they are catalysts for questioning and reformulating views of the natural world, help shape assessments of the veracity of a priori predictions about ecological trends and phenomena, and underpin questioning of effectiveness of resource management. Despite the importance of ecological surprises, major gaps in understanding remain about how studies might be done differently or done better to improve the ability to identify them. We outline the kinds of ecological surprises that have arisen from long-term research programs that we lead in markedly different ecosystems around the world. Based on these case studies, we identify important lessons to guide both existing studies and new investigations to detect ecological surprises more readily, better anticipate unusual ecological phenomena, and take proactive steps to plan for and alleviate "undesirable" ecological surprises. Some of these lessons include: (i) maintain existing, and instigate new, long-term studies; (ii) conduct a range of kinds of parallel and concurrent research in a given target area; (iii) better use past literature and conceptual models of the target ecosystem in posing good questions and developing hypotheses and alternative hypotheses; and (iv) increase the capacity for ecological research to take advantage of opportunities arising from major natural disturbances. We argue that the increased anticipatory capability resulting from these lessons is critical given that ecological surprises may become more prevalent because of climate change and multiple and interacting environmental stressors.

The quadruple squeeze: defining the safe operating space for freshwater use to achieve a triply green revolution in the anthropocene

Humanity has entered a new phase of sustainability challenges, the Anthropocene, in which human development has reached a scale where it affects vital planetary processes. Under the pressure from a quadruple squeeze-from population and development pressures, the anthropogenic climate crisis, the anthropogenic ecosystem crisis, and the risk of deleterious tipping points in the Earth system-the degrees of freedom for sustainable human exploitation of planet Earth are severely restrained. It is in this reality that a new green revolution in world food production needs to occur, to attain food security and human development over the coming decades. Global freshwater resources are, and will increasingly be, a fundamental limiting factor in feeding the world. Current water vulnerabilities in the regions in most need of large agricultural productivity improvements are projected to increase under the pressure from global environmental change. The sustainability challenge for world agriculture has to be set within the new global sustainability context. We present new proposed sustainability criteria for world agriculture, where world food production systems are transformed in order to allow humanity to stay within the safe operating space of planetary boundaries. In order to secure global resilience and thereby raise the chances of planet Earth to remain in the current desired state, conducive for human development on the long-term, these planetary boundaries need to be respected. This calls for a triply green revolution, which not only more than doubles food production in many regions of the world, but which also is environmentally sustainable, and invests in the untapped opportunities to use green water in rainfed agriculture as a key source of future productivity enhancement. To achieve such a global transformation of agriculture, there is a need for more innovative options for water interventions at the landscape scale, accounting for both green and blue water, as well as a new focus on cross-scale interactions, feed-backs and risks for unwanted regime shifts in the agro-ecological landscape.

Effects of discharge and local density on the growth of juvenile Atlantic salmon Salmo salar

The study explored the combined effects of density, physical habitat and different discharge levels on the growth of juvenile Atlantic salmon Salmo salar in artificial streams, by manipulating flow during both summer and winter conditions. Growth was high during all four summer trials and increased linearly with discharge and mean velocity. Differences in fish densities (fish m(-3)) due to differences in stream volume explained a similar proportion of the variation in mean growth among discharge treatments. Within streams, the fish aggregated in areas of larger sediment size, where shelters were probably abundant, while growth decreased with increasing densities. Fish appeared to favour the availability of shelter over maximization of growth. Mean growth was negative during all winter trials and did not vary among discharge treatments. These results suggest that increased fish densities are a major cause of reduced summer growth at low discharge, and that habitat-mediated density differences explain the majority of the growth variation across habitat conditions both during summer and winter.

Climate and vegetational regime shifts in the late Paleozoic ice age earth

The late Paleozoic earth experienced alternation between glacial and non-glacial climates at multiple temporal scales, accompanied by atmospheric CO2 fluctuations and global warming intervals, often attended by significant vegetational changes in equatorial latitudes of Pangaea. We assess the nature of climate-vegetation interaction during two time intervals: middle-late Pennsylvanian transition and Pennsylvanian-Permian transition, each marked by tropical warming and drying. In case study 1, there is a catastrophic intra-biomic reorganization of dominance and diversity in wetland, evergreen vegetation growing under humid climates. This represents a threshold-type change, possibly a regime shift to an alternative stable state. Case study 2 is an inter-biome dominance change in western and central Pangaea from humid wetland and seasonally dry to semi-arid vegetation. Shifts between these vegetation types had been occurring in Euramerican portions of the equatorial region throughout the late middle and late Pennsylvanian, the drier vegetation reaching persistent dominance by Early Permian. The oscillatory transition between humid and seasonally dry vegetation appears to demonstrate a threshold-like behavior but probably not repeated transitions between alternative stable states. Rather, changes in dominance in lowland equatorial regions were driven by long-term, repetitive climatic oscillations, occurring with increasing intensity, within overall shift to seasonal dryness through time. In neither case study are there clear biotic or abiotic warning signs of looming changes in vegetational composition or geographic distribution, nor is it clear that there are specific, absolute values or rates of environmental change in temperature, rainfall distribution and amount, or atmospheric composition, approach to which might indicate proximity to a terrestrial biotic-change threshold.

Turning back from the brink: detecting an impending regime shift in time to avert it

Ecological regime shifts are large, abrupt, long-lasting changes in ecosystems that often have considerable impacts on human economies and societies. Avoiding unintentional regime shifts is widely regarded as desirable, but prediction of ecological regime shifts is notoriously difficult. Recent research indicates that changes in ecological time series (e.g., increased variability and autocorrelation) could potentially serve as early warning indicators of impending shifts. A critical question, however, is whether such indicators provide sufficient warning to adapt management to avert regime shifts. We examine this question using a fisheries model, with regime shifts driven by angling (amenable to rapid reduction) or shoreline development (only gradual restoration is possible). The model represents key features of a broad class of ecological regime shifts. We find that if drivers can only be manipulated gradually management action is needed substantially before a regime shift to avert it; if drivers can be rapidly altered aversive action may be delayed until a shift is underway. Large increases in the indicators only occur once a regime shift is initiated, often too late for management to avert a shift. To improve usefulness in averting regime shifts, we suggest that research focus on defining critical indicator levels rather than detecting change in the indicators. Ideally, critical indicator levels should be related to switches in ecosystem attractors; we present a new spectral density ratio indicator to this end. Averting ecological regime shifts is also dependent on developing policy processes that enable society to respond more rapidly to information about impending regime shifts.