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Ensuring global food security and environmental sustainability is dependent upon the contribution of the world's hundred million smallholder farms, but the contributions of smallholder farms to global agricultural greenhouse gas (GHG) emissions have been understudied. We developed a localized agricultural life cycle assessment (LCA) database to calculate GHG emissions and made the first extensive assessment of the smallholder farms' GHG emission reduction potentials by coupling crop and livestock production (CCLP), a redesign of current practices toward sustainable agriculture in China. CCLP can reduce the GHG emission intensity by 17.67%, with its own feed and manure returning to the field as an essential path. Scenario analysis verified that greater GHG emission reduction (28.09%-41.32%) will be achieved by restructuring CCLP. Therefore, this mixed farming is a mode with broader benefits to provide sustainable agricultural practices for reducing GHG emissions fairly. ispartof: ISCIENCE vol:26 issue:6 ispartof: location:United States status: accepted

The flourishing logistics in both developed and emerging economies leads to huge greenhouse gas (GHG) emissions; however, the emission fluxes are poorly constrained. Here, we constructed a spatial network of logistic GHG emissions based on multisource big data at continental scale. GHG emissions related to logistics transportation reached 112.14 Mt CO

Ethiopian shade coffee plantations are well documented to be bird-friendly and act as refuges for disappearing tree species. The extent to which these plantations support mammal conservation, as well as mammal sensitivity to coffee intensification, remain little studied. We studied the distribution and diversity of mammals under three coffee management systems of differing intensities (i.e., semi-forest, semi-plantation, and plantation) and in nearby natural forests in Belete-Gera Forest Priority Area, southwestern Ethiopia. We detected mammals using 30 infrared camera traps at 90 stations for a total of 4142 camera days. We used the Shannon-Wiener diversity index for diversity analysis, generalized linear mixed model for comparison of independent detection, and non-metric multidimensional scaling to show the mammalian community composition. We recorded 8815 digital videos and a total of 23 mammal species. The overall species richness, diversity, and detection of mammals did not differ between the two traditional shade coffee management systems and the natural forest but was lower in the plantation coffee system. The mammal community composition also shows variation in resilience to coffee management intensity, with primates appearing to be generally more tolerant to management intensification. We ultimately show that traditionally managed Ethiopian shade coffee farms shelter diverse mammal communities, comparable to those in nearby natural forests. Therefore, supporting traditional coffee management practices and certifying them as mammal-friendly should be implemented as strategies for the conservation of mammals, as natural forests continue to decline in Ethiopia.

There are various ways to construct good processes for soliciting and understanding science. Our critique of advisory models finds that a well-supported chief science advisor (CSA) best ensures the provision of deliberative, informal, and emergency advice to government. Alternatively, bias, increasingly manifest as science-based advocacy, can hinder communication, diminish credibility, and distort scientific evidence.

In traditional ecological models, the effects of abiotic and biotic factors are often assumed to be monotonic, i.e. either positive, negative or neutral. However, there has been growing evidence that non-monotonic effects of environmental factors and both intra- and inter-specific interactions can significantly influence the dynamics and stability of populations, communities and ecosystems. In this paper, we present a review and synthesis on both theoretical and empirical studies on ecological non-monotonicity. There are various non-monotonic relations observed in populations, communities and ecosystems. The non-monotonic function of per capita population increase rate against intrinsic or extrinsic factors is a significant driving force in determining the complexity and stability of biological systems. There are several mechanisms such as the law of tolerance, adaptive behaviors, or opposing dual or pathway effects which may result in non-monotonic functions. Ecological non-monotonic functions are often closely related to spatial and temporal scale processes which may explain why ecosystems are often highly variable and unpredictable in both space and time. Recognizing ecological non-monotonicity would greatly change our conventional monotonic views on the effects of environmental factors and species interactions on ecosystems. We appeal for more effort to study ecological non-monotonicity and re-think our strategies to manage ecosystems under accelerated global change.

Understanding the causes of the large interannual fluctuations in the recruitment to many marine fishes is a key challenge in fisheries ecology. We here propose that the combination of mechanistic and statistical modelling of the pelagic early life stages (ELS) prior to recruitment can be a powerful approach for improving our understanding of local-scale and population-scale dynamics. Specifically, this approach allows separating effects of ocean transport and survival, and thereby enhances the knowledge of the processes that regulate recruitment. We analyse data on the pelagic eggs, larvae and post-larvae of Northeast Arctic cod and on copepod nauplii, the main prey of the cod larvae. The data originate from two surveys, one in spring and one in summer, for 30 years. A coupled physical–biological model is used to simulate the transport, ambient temperature and development of cod ELS from spawning through spring and summer. The predictions from this model are used as input in a statistical analysis of the summer data, to investigate effects of covariates thought to be linked to growth and survival. We find significant associations between the local-scale ambient copepod nauplii concentration and temperature in spring and the local-scale occurrence of cod (post)larvae in summer, consistent with effects on survival. Moreover, years with low copepod nauplii concentrations and low temperature in spring are significantly associated with lower mean length of the cod (post)larvae in summer, likely caused in part by higher mortality leading to increased dominance of young and hence small individuals. Finally, we find that the recruitment at age 3 is strongly associated with the mean body length of the cod ELS, highlighting the biological significance of the findings.

Mortality of pelagic eggs and larvae of marine fish is often assumed to be constant both in space and time due to lacking information. This may, however, be a gross oversimplification, as early life stages are likely to experience large variations in mortality both in time and space. In this paper we develop a method for estimating the spatial variability in mortality of eggs and larvae. The method relies on survey data and physical–biological particle-drift models to predict the drift of ichthyoplankton. Furthermore, the method was used to estimate the spatially resolved mortality field in the egg and larval stages of Barents Sea cod ( Gadus morhua ). We analyzed data from the Barents Sea for the period between 1959 and 1993 when there are two surveys available: a spring and a summer survey. An individual-based physical–biological particle-drift model, tailored to the egg and larval stages of Barents Sea cod, was used to predict the drift trajectories from the observed stage-specific distributions in spring to the time of observation in the summer, a drift time of approximately 45 days. We interpreted the spatial patterns in the differences between the predicted and observed abundance distributions in summer as reflecting the spatial patterns in mortality over the drift period. Using the estimated mortality fields, we show that the spatial variations in mortality might have a significant impact on survival to later life stages and we suggest that there may be trade-offs between increased early survival in off shore regions and reduced probability of ending up in the favorable nursing grounds in the Barents Sea. In addition, we show that accounting for the estimated mortality field, improves the correlation between a simulated recruitment index and observation-based indices of juvenile abundance.

There is limited statistical support for top-down effects on plankton in oceanic ecosystems. We quantify the combined effects of key planktivorous fish, invertebrates and climate on mesozooplankton dynamics in the Barents Sea. Zooplankton biomass was measured during Russian and Norwegian surveys in April–May and June–July 1959–1990 and August–early October (1981) 1984–2010. We found that zooplankton biomass in the central and northern Barents Sea in August–October showed pronounced multi-year fluctuations that were strongly negatively correlated with the total biomass of planktivorous fish. Fish predation explained >50% of the interannual variability in the biomass of medium-sized and large mesozooplankton in these parts of the Barents Sea and the predation effects remained significant while accounting for effects of climate variables. Spatiotemporal statistical analyses for different zooplankton size fractions supported the interpretation of top-down control, predominantly from capelin, on the zooplankton. In the southwestern Barents Sea the fluctuations were less pronounced and uncorrelated to total biomass of planktivorous fish, suggesting weaker top-down control by fish in this region, characterised by higher productivity and higher diversity of the predators. We suggest that predator-driven zooplankton fluctuations may play an important role in the ecosystem dynamics of the Barents Sea and potentially other Arcto-boreal shelves.

Climate may affect marine fish populations through many different pathways, operating at a variety of temporal and spatial scales. Climate impacts may work their way bottom up through the food web or affect higher trophic levels more directly. In this review we try to disentangle and summarize some of the current knowledge made available through the rapidly increasing literature on the topic, with particular emphasis on the work within the Global Ocean Ecosystems Dynamics (GLOBEC) programme. We first consider different classification schemes and hypotheses relating climate through physical features of the ocean to population patterns. The response of a population or community to climate may be linear or non-linear, direct or indirect. The hypotheses may be classified according to the form of physical features in operation as being related to mixing, advection or temperature. The bulk of the paper is devoted to a region-by-region presentation and discussion of examples relating climate variability to marine fish populations. It is slanted towards the North Atlantic and North Pacific, but the tropical Pacific is also covered. By means of different categorization methods we compare climate responses between ecosystems. We conclude that the use of such classification schemes allows for a more precise description of the various ecosystems particular properties and facilitates inter-regional comparison.

North-East Arctic cod is shared by Russia and Norway. Taking its multi-cohort structure into account, how would optimal management look like? How would non-cooperative exploitation limit the obtainable profits? To which extent could the strategic situation explain today’s over-harvesting? Simulation of a detailed bio-economic model reveals that the mesh size should be significantly increased, resulting not only in a doubling of economic gains, but also in a biologically healthier age-structure of the stock. The Nash equilibrium is close to the current regime. Even when effort is fixed to its optimal level, the non-cooperative choice of gear selectivity leads to a large dissipation of rents.

Walleye pollock (Theragra chalcogramma) is a commercially important marine fish in the Gulf of Alaska that has provided a natural experimental system to study many features of the recruitment process. We review recruitment of pollock in the Gulf of Alaska in the conceptual framework of a complex system. In this perspective, high frequency, or activating, events during egg and larval life introduce variability to the dynamics of the population, whereas lower frequency constraining processes tend to promote broader patterns. This view is supported by both simple population and complex statistical models that capture the trends and general patterns in the time series of recruitment. Consequences of this view of recruitment are discussed in terms of forecasting strategies. Published by Elsevier Ltd.

There has been a recent resurgence of interest in fisheries recruitment as a dynamic and complex process that is integrated over several life stages, with a variety of factors acting across scales to initiate, modulate, and constrain population abundance and variability. In this paper, we review the theory of recruitment phase transitions using a marine fisheries perspective. We propose that transitions in recruitment are dependent upon the balance of activating and constraining processes of recruitment control, and we highlight fundamental differences in recruitment transitions precipitated by climate events, those related to community alterations, and those manifested by fishery practices (though each is not necessarily mutually exclusive). We maintain that the emergent properties of fisheries populations post-phase transition are contingent upon their histories, their differing initial states, the degree of food web complexity, interaction strengths among interspecifics, and contrasting external forcing, any or all of which may be dissimilar between one regime and another. We suggest that it may be challenging to forecast recruitment phase transitions, though we encourage efforts to determine whether there are unifying relationships that govern recruitment dynamics.

The growth and survival of woody seedlings in arid and semi-arid riverine forests is partly determined by the ability of their roots to maintain contact with the alluvial water table. After a flood event, the water table declines in conjunction with the river stage and the rate of decline may have species-specific effects on the regeneration of riverine trees. In this study, a growth experiment involving seedlings of Acacia tortilis and Faidherbia albida, two keystone tree species along the regulated Turkwel River in northern Kenya, was conducted to assess the effects of simulated pre- and post-dam water table dynamics. Seedlings were grown in rhizopods with constantly shallow water tables (0 cm day−1 treatment), slow rates of water table decline (5 cm day−1 treatment), rapid rates of water table decline (10 cm day−1 treatment) and no subsurface water (rainfall treatment). The last treatment corresponded to the dam-induced paucity of floodplain inundation but allowed early seedling growth in response to rainfall. Results showed that F. albida attained larger shoot growth but shorter root lengths than A. tortilis, while water table decline promoted root elongation in both species. However, F. albida seedlings were adversely affected by moisture deficits under the rapid rate of water table decline and rainfall treatments. In contrast, the growth of A. tortilis seedlings was sustained under all treatments, suggesting that A. tortilis is a drought tolerant facultative phreatophyte, while F. albida behaves more like a near obligate phreatophyte. For F. albida, the ideal stage recession rate following a flood event is 5 cm day−1 or less, which is also favourable for A. tortilis. Although more research is still needed on the hydrological preferences of woody seedlings in the Turkwel River floodplain, it is evident that the regeneration of strictly riverine trees such as F. albida depends on slow rates of water table decline in the post-flood period.

The aim of this paper was to determine how the abundance of species of the flagellate genus Chrysochromulina (Haptophyta) varies in relation to environmental conditions and season in a coastal area of the Skagerrak in southern Norway. The study was based on a fourteen-year time series (1989–2002) comprising data on Chrysochromulina spp. abundance, temperature, salinity, and nutrient and chlorophyll-a concentrations. Environmental data were aggregated by depth and season, and Chrysochromulina abundance was expressed as annual average abundance, which was positively correlated to annual maximum abundance. The main seasonal occurrence of Chrysochromulina was between April and August, but the abundance displayed strong short-term (days) and inter-annual variation. Annual average abundance of Chrysochromulina species was positively and significantly correlated with spring and summer N:P (nitrate/phosphate) ratios, and negatively and significantly correlated with summer salinity and summer phosphate concentration. The analysis indicates that high and skewed spring N:P ratios, stratified conditions with a low salinity surface layer during summer together with low phosphate concentrations are associated with favourable conditions for Chrysochromulina .

The ecology of arid and semi-arid floodplain forests in Africa is being deliberately altered by the construction of dams. There is, however, a widespread lack of baseline data to support detailed assessments of dam-induced impacts on downstream forest composition. In the Turkwel River, north-western Kenya, fragmented discharge records reveal that the river flow regime has changed significantly after the impoundment of the Turkwel Gorge Dam in 1990. In order to generate hypotheses on the impacts of river damming, a series of 93 sample plots (30 m × 30 m) were distributed across and along the entire Turkwel River floodplain. The vegetation gradients were summarized by detrended correspondence analysis and correlated with measured environmental variables. Canonical correspondence analysis was then used to partition the compositional variation on hydrological, climatic, land-use, and edaphic variables. The gradient approach was compared with the scales of spatial autocorrelation among ordination axes and environmental variables to detect causal vegetation-environment relationships. Results show that the main vegetation gradient was strongly correlated with distance to the river channel, elevation, and subsoil electrical conductivity, while the second gradient was strongly correlated with distance to the river mouth and rainfall. Increased lateral distance and elevation was interpreted as a reduction in flooding frequency and duration towards the dry and saline edge of the riverine zone. Floodplain inundation is believed to combine with post-flood water tables in determining suitable conditions for forest regeneration. The longitudinal gradient represented a regional change in water regime from the mesic upstream to the xeric downstream section of the river. Variation partitioning illustrated the crucial importance of hydrology, which explained 63% of the total compositional variation, as compared to soils (43%), climate (34%), and land-use (4%). There were also significant interactions between hydrology, soils, and climate. It is hypothesised that the Turkwel riverine forest will experience shifts in the lateral as well as longitudinal vegetation gradients due to reductions in peak and mean flows. This study demonstrates an efficient and straightforward approach for assessing the possible impacts of river flow regulation in the absence of detailed hydrological data and long-term vegetation records.

Perceptions on the role played by shifting agriculture on ecosystems integrity at the landscape scale are divided between those proposing loss of biodiversity and habitat fragmentation and those suggesting improvement of ecosystem diversity. This study investigated the impacts of sorghum (Sorghum bicolour (L.) Moench) cultivation in farming landscapes divided between active and fallow farms in the 120 km2 floodplain of the lower Turkwel River, northwestern Kenya. Farming landscapes were grouped into: recently farmed (

In the arid zone of central Turkana, north-western Kenya, where soil salinity affects 15–20% of the rangelands, growth performances of trees planted in saline soil rehabilitation trials have not been evaluated. Tree-planting trials have emphasised exotic species over indigenous ones. However, advantages and disadvantages of promoting exotic tree species have not been examined. The current study was aimed at evaluating growth performance of seven exotic and nine indigenous tree species used in saline soil rehabilitation trials. The tree species were established from 6-month-old saplings using microcatchments (FT1) from 1988 through 1990 and pitting treatment (FT2) from 1989 through 1992. The soils in FT1 and FT2 treatments were moderately to highly saline. The exotic tree species produced greater cover and volume during the first year (FT1) but by the second year, production was not sustained due to greater mortality (FT1 & FT2). The indigenous species in general had higher survival rates. Relative growth rates (RGR) of exotic and indigenous species did not differ (FT1 & FT2). Tree mortality was negatively correlated with RGR for exotic species in FT1 but not for indigenous ones. However, changes in plant performance were not in response to salinity alone. Rather, water scarcity superimposed on soil salinity might have influenced plant growth performance. Greater water and salinity stress and subsequently greater mortality in exotic species provided a more convincing reason for promotion of indigenous tree species. In the future, knowledge of salinity distribution and selection of indigenous species to match this will be a better way of rehabilitating sites affected by soil salinity in the arid zone of central Turkana, north-western Kenya.

In a widely received study (Science 321: 1678–1681) Costello and his colleagues found that catch shares give better stock persistence and higher catch for fishermen. The conclusions made by Costello et al were further being supported by Grafton and McIlgrom (Marine Policy 33: 714– 719) where they suggested a framework in order to determine the costs and benefits of separate ITQ management in seven Australian commonwealth fisheries, and what the alternatives should be if the net benefits do not justify ITQs. This raises the question why we do not see catch shares being used more often. We explore at a global scale which countries would have the potential for – and indeed do fulfil the conditions necessary to implement such a management strategy.

The objectives pursued by governments managing fisheries may include maximizing profits, minimizing the impact on the marine ecosystem, or securing employment, which all require adjusting the composition of the fishing fleet. We develop a management plan that can be adapted to those objectives and allows the regulator to compare the long-run profits between the various management options. We apply the model to the case of Northeast Arctic cod, and estimate the cost and harvesting functions of various vessel types, the demand function, and a biological model to provide key insights regarding the optimal management of this valuable fish species.

Mathematical models are developed in order to analyze whether or not social factors, such as, for example, the “social fence” ( J. B. Hestbeck, 1982 , Oikos 39 , 157–163) will stabilize population density: the dynamic interaction between social factors and (dynamic) trophic factors is analyzed. It is concluded that social factors such as the “social fence” tend to stabilize population density; hence, if density cycles (as, e.g., seen in many microtine rodents) are observed in nature, it seems reasonable to conclude that density cycles are driven by, for example, trophic interactions and not by social factors. It is suggested that the “social fence” may explain why so many populations including several microtine populations have fairly stable densities despite the ever-existing destabilizing trophic interactions. Contrary to what is implied by J. B. Hestbeck (1983 , “A Mathematical Model of Population Regulation in Cyclic Mammals,” Lecture notes in biomathematics, Vol. 52, Springer-Verlag, Berlin/New York), the analysis presented in this paper demonstrates that seasonal environmental changes are not essential for the generation of regular density cycles. Seasonal changes may, however, be necessary for generating a microtine- like density cycle. Empirical information on microtine rodents relating to the “social fence hypothesis” is discussed.

By linking optimal foraging theory and optimal life history theory, we demonstrate that optimal diets, in general, may depend on the individual's age even when everything else remains the same. Older individuals (i.e., individuals with lower reproductive values) are predicted to have diets composed of highly nutritious food types that are possibly dangerous to pursue.

Optimal demographic strategies (life histories of l x - m x schedules) for populations with stable and cylicly varying densities are predicted on the basis of a density dependent population dynamics model; the cyclic density pattern—often seen in lemmings and voles —is assumed to have relatively slow density increase followed by an abrupt density crash. Analysis shows that low reproductive rates for all ages and a Type I or II survival schedule will be favored by natural selection in stable populations. High reproductive rates for all ages and a Type III survival schedule will be favored by natural selection in cyclic populations. These strategies may be regarded as the endpoints of a continuum. Features predicted to be optimal for opportunistic species are expected to be more pronounced the more hostile the environment is. Since all quantities used in formulating these predictions are operationally defined, the predicted patterns are testable. Predictions derived from the model are compared, in a general way, with available data. This comparison suggests the validity of the theory.

A mathematical model for studying the evolution of optimal life histories is presented. This model explicitly incorporates the population dynamics of the organism under evolution. Reproductive strategies in cyclic (or opportunistic) and stable (or equilibrium) populations are compared. A continuum of different kinds of population dynamics patterns may be obtained, the extremes of which are the opportunistic and equilibrium strategies (or species). Our analysis further predicts that more resources should be devoted to reproduction than to competitive abilities in an opportunistic species. For equilibrium species, the allocation priorities should be reversed. Predictions from the theory are compared with data on small rodent species exhibiting regular density variations.

Optimal foraging theory is extended so as to treat cases where a choice between several options is required. A new version of optimal foraging theory is derived under this assumption of simultaneous encounters of prey species and proved by using a set-theoretic approach. On the basis of this new version, it is demonstrated that, in general, no unique ranking of food types can be specified only from knowledge of the intrinsic properties of the food types. It is demonstrated that a food type may become less frequent in the diet as a result of becoming more abundant in the environment; that an increase in the abundance of a food type represented in the diet may have the effect that new food types enter the diet; and that an increase in the overall food abundance may imply that new types are included and/or old ones are excluded.

A general method for locating an evolutionarily stable strategy (ESS) in ecological models is developed. By comparing the fitness of an established (or wild-) type with that of a potential invading mutant type, a sufficient condition for the wildtype to be an ESS is obtained with reference to an invasion matrix , a form of community matrix. In the simplest case this is the same as requiring that the specific growth rate (or reproductive fitness) of the mutant is positive when it first arises. The mathematical and biological conditions for the validity of this equivalence are discussed.

Most current models for optimal food selection apply to ecological and behavioural optimization. In this paper optimal food selection theory is extended to apply to evolutionary optimization. A general evolutionary model for optimal food selection must incorporate the concept of fitness sets--or that variables, changing as a result of natural selection in evolutionary time, cannot, in general, vary independently of each other. A "Charnov type" optimal food selection model with a fitness set is investigated, and evolutionarily stable strategy (ESS) solutions of the evolutionary variables (i.e., the efficiencies of using available food types) are found. From this analysis it follows that the relative frequency of various food types in the environment may, under specified conditions, influence the evolutionarily optimal diet. Secondly, the analysis demonstrates that a food type not in the optimal diet may, in evolutionary time, be added to this by becoming more abundant. Thirdly, it follows from the analysis that the ecological result of MacArthur and Pianka, that food types are worth eating even if there is competition for them, is not generally applicable when referring to an evolutionary time scale. Finally, it is pointed out that for the diet to be an ESS, it is necessary that the consumer's density is stable and that the consumer's population dynamics are subjected to some density-dependent factor.

Models for the evolution of cannibalism through natural selection are discussed. The models are analysed by the technique of seeking evolutionarily stable strategies (ESS). The main analysis is carried out with only one evolutionary variable—the degree of cannibalism. Cannibalism is, particularly in stable populations, expected to evolve if the young stages being cannibalized have low reproductive potential, and if the reproductive output of the older, cannibalistic stages is high. Analysis further indicated that cannibalism is particularly likely to evolve in cases where only a few age-classes are cannibalized, and when the reproductive output is concentrated in the last part of reproductive age. Analysis also indicates that K -selected species are more likely to be cannibals than r -selected species.

Character displacement of competing species is studied. A model, originally developed by MacArthur and Levins (Proc. Natl. Acad. Sci. USA 51 (1964), 1207–1210) and further analyzed by Lawlor and Maynard Smith (Amer. Nat. 110 (1976), 70–99), has been reanalyzed. In the present paper, a more formally correct analysis of the MacArthur-Levins model is provided. A standard population genetics approach to sexually reproducing populations is adopted. The same conclusion as proposed by Lawlor and Maynard Smith emerges; competition can lead only to character divergence. In our analysis we either require that allopatrically evolved consumer populations must be able to coexist at an ecologically stable equilibrium (hence, we require mutual invasibility), or consider the feasibility of allopatric equilibria.

Population dynamics is rarely considered in current pest control programs. Instead of the usual aim of killing a certain percentage of the target species, we demonstrate here the importance of considering dynamic aspects of populations when attempting management (e.g., pest control) of vertebrate populations. Conceptually we treat heterogeneous landscapes with pest-suitable patches intermingled with non-suitable areas. These pest-suitable patches are also regarded as separate objects for local pest management. We discuss density-independent and density-dependent natality and mortality rates for separate patches. In the landscape context we treat immigration into, and extinction in local patches. In this analysis we also consider the importance of transition habitats for local and regional population development. We summarize our conclusions in a list of features which ought to be examined before a species' pest status can be evaluated and management programs are planned. Important information for such a purpose is the form and magnitude of natural mortality rates as functions of density, magnitude of equilibrium densities, the occurrence of presaturation dispersal or not, and the costs of reducing natality and of increasing mortality. Due to the immature state of population ecology, we emphasize that our suggestions have to be regarded as hypotheses to be tested in actual management situations.