Ecological monitoring to support Water Sharing Plan evaluation and protect wetlands of inland New South Wales,Australia

Government‐funded flow response monitoring and modelling programmes (flow science) provided by the New South Wales Office of Water (NOW) have supported water resource management since 1997. Flow science has a core technical component defined by hypothesis‐driven long‐term monitoring and analysis, but it also represents many activities that support committees involved in environmental flow management. This is done through collaborations and contracting and has fostered considerable research and analysis into flow ecology, including modelling for the recent Murray–Darling Basin Plan. We describe the performance of environmental flows against legislated wetland objectives to improve wetland function and diversity using flow science. On‐ground monitoring at wetland sites has largely ceased but the flow science done so far indicates that the environmental flow rules written into Water Sharing Plans improve wetland diversity and function. Determination of the long‐term flow needs of NSW wetlands, including how well current Water Sharing Plans aid the delivery of environmental flows, requires finding the means to build on current flow science knowledge from across Australia.     

Emergy evaluations of three aquaculture systems on wetlands surrounding the Pearl River Estuary,China

Emergy and economic analysis, accompanied by sensitivity analysis, were used to evaluate the ecological economic characteristics of three fish aquaculture systems on wetlands surrounding the Pearl River Estuary in China. The sustainability of these systems was compared to two aquaculture systems and two wetland systems, to provide reference conditions for the best use of limited wetland areas. We found that the three systems studied had similar emergy characteristics, despite their very different economic characteristics. Counter intuitively, the high economic input and output mode did not have higher environmental impact or lower sustainability compared with low economic input and output mode. Apparently, the sustainability of an intensive aquaculture system is determined mainly by how many natural renewable resources are exploited. The large differences in economic benefit and environmental impacts between the mangrove reserve and the aquaculture systems demonstrated the important role of nature reserves on preserving the sustainability of an estuary. Transformity (TR) and Emergy Yield Ratio (EYR) are both indicators of system efficiency, but from different points of view, and they produced opposite results in assessing the efficiency of the same system in this study. The ratio of EYR to TR might be used in addition to the EYR and transformity as a discreet perspective on overall system production efficiency.     

Differences exist in bird communities using restored and natural wetlands in the Parkland region,Alberta, Canada

Wetland restoration is used to compensate for historic and ongoing wetland losses. We compared bird community composition in 24 restored wetlands and 36 natural wetlands in the Parkland region of Alberta. Natural wetlands ranged in exposure to agricultural activity and were binned into three classes (low, medium, and high disturbance). Although the abundance and average species richness of birds were similar between restored and natural wetlands (analysis of variance: p > 0.22), the avian community composition differed significantly among wetland types (multiresponse permutation procedure [MRPP]: A = 0.05, p < 0.001). The avifauna using restored wetlands was distinct from the avifauna using natural wetlands spanning a range of disturbance levels (A = 0.02–0.06; p ≤ 0.006). Notably, restored wetlands were surrounded by less shrub/forest cover and more open water than low‐disturbance, natural wetlands. The majority (58%) of species using the surveyed wetlands were not classified as wetland‐dependent. Interestingly, if only wetland‐dependent species are considered, the avifauna using restored wetlands is no longer distinctive (MRPP: A < 0.01, p = 0.187), although the abundance of wetland‐dependent birds was marginally higher in restored wetlands (n = 24) than in low‐disturbance, natural wetlands (n = 10; Tukey's honestly significant difference test: p = 0.041). Overall, restored wetlands had reduced beta diversity compared to natural wetlands, regardless of whether the avifauna were restricted to wetland‐dependent species or considered comprehensively. This draws into question the legitimacy of the assumption that restoration can fully offset continued losses of natural wetlands.     

Aspects of wetland law and policy in Australia

The existence of laws and policies in Australia that affect wetland protection and rehabilitation has been ascertained. There is a diverse range of environmental legislation, primarily at the state level, that potentially affects wetlands. There are environmental planning instruments made under legislation in New South Wales and Western Australia, which are specifically directed to the protection of wetlands. These are legislative-backed mechanisms providing legal protection to wetlands. Whilst there is no national policy on wetlands, a draft Commonwealth policy has been circulated and is expected to be released in final form in February 1997. New South Wales is the only state with a current wetlands policy, whilst some other states have draft policies. These policies do refer to wetland rehabilitation. The present federal government indicated it wished to finalize a national wetlands policy in the lead up to its election in March 1996. This is not likely to happen soon and any national policy will probably be an implementation framework for the policies of individual governments. It is suggested that a commonwealth policy, whilst useful in providing consistency in commonwealth government decision making affecting wetlands, does not go far enough. Given that only one state in Australia has a wetland policy, it may take the formulation of a national policy to get the remaining states and territories in Australia to finalize their own policies.     

A synthesis of methane emissions from 71 northern,temperate, and subtropical wetlands

Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database of approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general controls on wetland methane emissions from soil temperature, water table, and vegetation, but also show that these relationships are modified depending on wetland type (bog, fen, or swamp), region (subarctic to temperate), and disturbance. Fen methane flux was more sensitive to vegetation and less sensitive to temperature than bog or swamp fluxes. The optimal water table for methane flux was consistently below the peat surface in bogs, close to the peat surface in poor fens, and above the peat surface in rich fens. However, the largest flux in bogs occurred when dry 30‐day averaged antecedent conditions were followed by wet conditions, while in fens and swamps, the largest flux occurred when both 30‐day averaged antecedent and current conditions were wet. Drained wetlands exhibited distinct characteristics, e.g. the absence of large flux following wet and warm conditions, suggesting that the same functional relationships between methane flux and environmental conditions cannot be used across pristine and disturbed wetlands. Together, our results suggest that water table and temperature are dominant controls on methane flux in pristine bogs and swamps, while other processes, such as vascular transport in pristine fens, have the potential to partially override the effect of these controls in other wetland types. Because wetland types vary in methane emissions and have distinct controls, these ecosystems need to be considered separately to yield reliable estimates of global wetland methane release.     

Land‐use and isolation interact to affect wetland plant assemblages

Different management regimes imposed on similar habitat types provide opportunities to investigate mechanisms driving community assembly and changes in species composition. We investigated the effect of pasture management on vegetation composition in wetlands with varying spatial isolation on a Florida cattle ranch. We hypothesized that increased pasture management intensity would dampen the expected negative effect of wetland isolation on native species richness due to a change from dispersal‐driven community assembly to niche‐driven assembly by accentuated environmental tolerance. We used native plant richness, exotic plant richness and mean coefficient of conservatism (CC) to assess wetland plant assemblage composition. Sixty wetlands were sampled, stratified by three levels of isolation across two pasture management intensities; semi‐native (less intensely managed; mostly native grasses, never fertilized) and agronomically improved (intensely managed, planted with exotic grasses, and fertilized). Improved pasture wetlands had lower native richness and CC scores, and greater total soil phosphorus and exotic species coverage compared to semi‐native pasture wetlands. Increased wetland isolation was significantly associated with decreases in native species richness in semi‐native pasture wetlands but not in improved pasture wetlands. Additionally, the species–area relationship was stronger in wetlands in improved pastures than semi‐native pastures. Our results indicate that a) native species switch from dispersal‐based community assembly in semi‐native pastures to a species‐sorting process in improved pastures, and b) recently‐introduced exotic species already sorted for more intensive management conditions are primarily undergoing dispersal‐based community assembly. That land‐use may alter the relative importance of assembly processes and that different processes drive native and exotic richness has implications for both ecosystem management and restoration planning.     

Upper Mississippi River restoration: implementation,monitoring, and learning since 1986

Upper Mississippi River Restoration (UMRR) was implemented to monitor environmental status and trends and restore degraded habitat. There was little experience conducting restoration in large rivers, and engineering and ecological integration evolved through project implementation. Loss of depth in backwaters and side channels, excessive biological oxygen demand, increased currents, and low water temperatures were common symptoms of backwater eutrophication that were primary objectives for implementing UMRR. Biological outcome monitoring was initially funded for six projects using the most common methods to restore aquatic and wetland habitat. UMRR island construction occurred as four generations of learning. Current plans represent a comprehensive restoration approach including: physical process modeling (i.e. hydraulic and wind‐wave modeling) of existing conditions and alternative restoration measures. Habitat Rehabilitation and Enhancement Projects, fish response monitoring validated winter habitat suitability models. Long term fish population monitoring indicates sustainable recovery, and now population interaction among restored lakes is under investigation. Isolated wetland management in Illinois River backwater lakes can achieve bottom consolidation that promotes emergent wetland habitat response that migratory waterfowl exploit in large numbers. Adult fish movement between the river and management units is restricted to flood stage or through control structures and post‐project movements into the lake for overwintering were not apparent. The lack of Illinois River overwintering habitat is shown by an abundance of young fish and few older fish in status and trends monitoring. Upper Mississippi River System ecosystem restoration practitioners have implemented ecosystem restoration science and practice in a manner that exemplifies the best intent of adaptive management.     

Where the fish swim above the birds: configurations and challenges of wetland restoration in the Po Delta,Italy

Wetland and estuary restoration presents a number of complex challenges that are primarily social, cultural, economic, and governance‐related rather than ecological. Here we consider the case of wetland restoration in the Po Delta, Italy. Wetland restoration of the Po Delta is a goal of a broad range of actors in the region and this project is a response to local calls for action. We investigate why local stakeholders are unsatisfied with apparently successful restoration projects, and appraise the factors that favor both the fulfillment of environmental targets and establishment of cooperative relations. We suggest that historical legacies of land use in the Po Delta have influenced current governance practices in a complex and fragmented governance context. Also, patterns of wetland restoration and wetland management practices differ between wetland types, and their outcomes may be influenced by the number of stakeholders involved, funding, and ability to generate direct revenues from management. However, there seem to be no blueprint solutions to successful wetland management and wetland restoration, and results are uneven at the landscape scale and often depending on contingencies. Maintaining traditional practices that retain cultural importance may be seen as part of restoration by local people. As a landscape that is highly anthropogenic and in continuous motion, we argue that the Delta exemplifies some of the challenges that restoration will face in a world increasingly characterized by novel ecosystems. We suggest actions that could contribute to enhancing wetland restoration outcomes in the Po Delta.     

全球环境变化对典型生态系统的影响研究:现状、挑战与发展趋势

随着全球环境变化和人类活动对生态系统影响的日益加深,生态系统结构和功能发生强烈变化,生态系统提供各类资源和服务的能力在显著下降。在这种背景下,全面认识生态系统的结构功能与全球环境变化的关系已成为当前生态学研究的热点之一。本文综述了全球环境变化对典型生态系统(包括森林生态系统、河口湿地生态系统、城市生态系统)影响以及全球环境变化适应的研究现状,分析研究面临的困难及挑战。在此基础上,提出对未来研究发展趋势的展望。在森林生态系统与全球环境变化研究上,未来应重视能更好模拟现实情景的、多因子、长期的全球环境变化控制试验,并注重不同生物地球化学循环之间的耦合作用。在湿地生态系统与全球环境变化研究上,未来应加强氮沉降、硫沉降及盐水入侵对湿地生态系统碳氮循环的影响,明晰滨海湿地的蓝碳功能,加强极端气候和人类干扰影响下湿地生态系统结构和功能变化及恢复力的研究。在城市生态系统与全球环境变化研究上,未来应深化城市生物地球化学循环机制研究,实现城市生态系统的人本需求侧重与转向,并开展典型地区长期、多要素综合响应研究。在全球环境变化适应研究上,未来应构架定量化、跨尺度的适应性评价体系,加强典型区域/部门的适应性研究以及适应策略实施的可行性研究,注重适应与减缓对策的关联研究及实施的风险评估。期望本综述为我国生态系统与全球环境变化研究提供一些参考。     

Eco‐efficiency Based on Social Performance and its Relationship with Financial Performance

As corporate responsibility for environmental management has gained attention, eco‐efficiency has become recognized as an important concept for improving the social performance of the business sector as well as that of the public sector. Improving eco‐efficiency is widely accepted not only as a means of increasing economic value, but also as a means of reducing environmental effects. However, managing for eco‐efficiency should take into consideration the differences among industries, because the impact of eco‐efficiency on financial and social performance varies among industries. To explore this variation, we conducted a cross‐industry analysis of eco‐efficiency based on social performance using data envelopment analysis (DEA). DEA measures relative efficiency and is a useful tool for taking into account the relative importance of industry‐specific characteristics. Using DEA, eco‐efficiency scores were derived based on the ratio of two factors of social performance: (1) value‐added inducing and production‐inducing economic spillover effects and (2) the amount of greenhouse gases emitted and energy used. Then, we identified the relationships between our eco‐efficiency score and financial performance, which is a measure of the firm's stability. The case study is based on 272 firms in 16 industries in South Korea. Results show that firms in product manufacturing and service‐intensive industries tend to have higher eco‐efficiency scores than those in raw material or chemical‐intensive industries. In addition, most of the industries reveal no relationship between traditional financial performance metrics and eco‐efficiency scores. A handful of industries had significant relationships with one or more financial performance metrics; in some cases, these relationships were negative, whereas in others they were positive. Surprisingly, almost all industries have no significant relationships between eco‐efficiency and financial performance. This result implies that government support for policies that reward firms that attempt to be eco‐efficient are needed, or that other nonfinancial metrics that influence eco‐efficiency, such as employment and brand reputation, should be considered. This article is expected to support policy makers as they formulate industry‐specific environmental strategies.     

Jump‐starting coastal wetland restoration: a comparison of marsh and mangrove foundation species

During coastal wetland restoration, foundation plant species are critical in creating habitat, modulating ecosystem functions, and supporting ecological communities. Following initial hydrologic restoration, foundation plant species can help stabilize sediments and jump‐start ecosystem development. Different foundation species, however, have different traits and environmental tolerances. To understand how these traits and tolerances impact restoration trajectories, there is a need for comparative studies among foundation species. In subtropical and tropical climates, coastal wetland restoration practitioners can sometimes choose between salt marsh and/or mangrove foundation species. Here, we compared the early life history traits and environmental tolerances of two foundation species: (1) a salt marsh grass (Spartina alterniflora) and (2) a mangrove tree (Avicennia germinans). In an 18‐month study of a recently restored coastal wetland in southeastern Louisiana (USA), we examined growth and survival along an elevation gradient and compared expansion and recruitment rates. We found that the rapid growth, expansion, and recruitment rates of the salt marsh grass make it a better species for quickly establishing ecological structure at suitable elevations. The slower growth, limited expansion, and lower recruitment of the mangrove species show its restricted capacity for immediate structural restoration, especially in areas where it co‐occurs with perennial salt marsh species. Our findings suggest that the structural attributes needed in recently restored areas can be achieved sooner using fast‐growing foundation species. Following salt marsh grass establishment, mangroves can then be used to further assist ecosystem development. This work highlights how appropriate foundation species can help jump‐start ecosystem development to meet restoration objectives.     

Influence of area,habitat and water chemistry on richness and composition of macrophyte assemblages in southern Brazilian wetlands

Questions: Two hypotheses were tested: (1) physical features, such as wetland surface area and habitat diversity, together with water chemistry, are important determinants of species richness and composition of macrophyte assemblages and (2) species richness and composition of macrophyte assemblages differ between wetlands of different types (i.e., palustrine versus lacustrine) and between wetlands of different hydrologies (i.e. permanent versus intermittent). Location: A subtropical coastal plain segment (2500 km²) of southern Brazil. Methods: Quarterly collections were carried out in 15 wetlands (2004–2005) in southern Brazil. Differences in richness over time were tested using repeated measures ANOVA. Stepwise multiple regression was performed to investigate relationships between total richness and environmental variables. Significance of differences between wetland types and hydroperiods on species composition was verified by MRPP (Multi‐Response Permutation Procedure). The influence of the environmental variables on species composition was assessed using CCA (Canonical Correspondence Analysis). Results: Macrophyte species richness changed with time, was not significantly different between wetland types, but was higher in permanent wetlands than in intermittent ones. Area, habitat diversity and soluble reactive phosphorus concentration explained 76% of the variation in species richness. Species composition was different between permanent and intermittent wetlands, although it was not significantly different between wetland types. Area, habitat diversity and water chemistry explained 50.1% of species composition. Conclusions: Species richness and composition of wetland macrophytes were mainly determined by area, habitat diversity and hydroperiod. These results can be used for the development of conservation and management programs in southern Brazil.     

Mitigation under Section 404 of the Clean Water Act: where it comes from, what it means

The requirement to mitigate impacts to wetlands and streams is a frequently misunderstood policy with a long and complicated history. We narrate the history of mitigation since the inception of the Clean Water Act Section 404 permit program in 1972, through struggles between the US Environmental Protection Agency and the US Army Corps of Engineers, through the emerging importance of wetland conservation on the American political landscape, and through the rise of market-based approaches to environmental policy. Mitigation, as it is understood today, was not initially foreseen as a component of the Section 404 permitting program, but was adapted from 1978 regulations issued by the Council on Environmental Quality as a way of replacing the functions of filled wetlands where permit denials were unlikely. EPA and the Corps agreed in 1990 to define mitigation as the three steps of avoidance, minimization, and compensation, principles which must be applied to permit decisions in the form of the environmental criteria in EPA’s 404(b)(1) Guidelines. Through the 1980s and 1990s, the compensation component of mitigation has become nearly the sole focus of mitigation policy development, and has been the subject of numerous guidance documents and memoranda since 1990. Avoidance and minimization have received far less policy attention, and this lack of policy development may represent a missed opportunity to implement effective wetland conservation.

湿地植物根形态结构和泌氧与盐和重金属吸收、积累、耐性关系的研究进展

目前大面积湿地面临着重金属污染和盐渍化问题.利用湿地植物修复这些受损生态系统和提高海水稻的产量、减少毒性金属元素在稻米中的积累是当前面临的重要任务.湿地植物(包括水稻)已发展出各种策略和机制来耐受不同的环境胁迫,它们的根系发育具有可塑性,如根形态和解剖结构会随外界条件的变化而变化,这些变化直接影响其对环境胁迫的适应性能...     

Macroinvertebrate community convergence between natural,rehabilitated, and created wetlands

Wetland restoration practices can include rehabilitating degraded wetlands or creating new wetlands. Empirical evidence is needed to determine if both rehabilitated and created wetlands can support the same macroinvertebrate communities as their natural counterparts. We measured long‐term macroinvertebrate community change in seasonal wetlands known as Delmarva Bays in Maryland, U.S.A. We compared a rehabilitated, a created, and a natural Delmarva Bay. We hypothesized that the created and rehabilitated wetlands would develop different macroinvertebrate communities. We also hypothesized that the community composition of the rehabilitated wetland would become more similar to that of the natural wetland than to that of the created wetland over 9 years encompassed by this study. We monitored the macroinvertebrates, including both predators and primary consumers, and environmental conditions in the three wetlands from March to August in 2005, 2006, 2007, and 2012. Cluster analysis indicated that from 2005 to 2007, the macroinvertebrate community of the rehabilitated wetland and the created wetland were more similar to each other than to the natural wetland. In 2012, the rehabilitated wetland was more similar to the natural wetland than to the created wetland. This similarity was driven principally by changes in the composition of primary consumer taxa. Our results suggest that rehabilitated Delmarva Bays are more likely to support a natural macroinvertebrate community than are created wetlands. Restoration practices that rehabilitate existing wetlands may be preferred over practices that create new wetlands when restoration project goals include developing natural macroinvertebrate communities in a short period of time.     

Effects of area,environmental status and environmental variation on species richness per unit area in Mediterranean wetlands

Abstract. We propose a mechanistic model to relate α- and γ-diversity to area per se, moisture status and environmental variation (local and total), and explored the effects these abiotic variables have on species richness per unit area (α-diversity) for plant communities in a network of wetland habitats located in a Mediterranean mountainous region of central Spain. In this study, environmental status is measured as actual evapotranspiration (as an expression of energy), slope and soil wetness, and environmental variation refers to slope variation and soil wetness variation. Species richness per unit area was related to soil wetness, soil wetness variation, ground slope and ground slope variation. There were also positive correlations among moisture status and environmental variation variables. There is a joint effect of slope and soil wetness variation in explaining species richness per unit area of these wetland habitats, but area effects and energy are relatively unimportant. We conclude that species richness per unit area of wetland vegetation can be explained by moisture status and local environmental variation, and that habitat area may not have an important effect. Area could affect γ-diversity directly through random sampling and/or indirectly through increasing β-diversity, and energy may be important in areas with larger energy ranges. Complete surveys of environmental status, local and total environmental variation, and their associated species assemblages are needed to explain the processes that give rise to the rule that larger areas have larger species richness.     

Environmental weeds in Australia and New Zealand: issues and approaches to management

Environmental weeds are plants that invade natural ecosystems and are considered to be a serious threat to nature conservation. Australia and New Zealand, where biota with a high degree of endemism have evolved, are particularly susceptible to environmental weeds. Environmental weeds have been implicated in the extinction of several indigenous plant species, and they also threaten ecosystem stability and functional complexity. Historically, emphasis has been placed on the chemical or manual ‘control’ of weed infestations, often with little consideration of the long‐term effectiveness or the ecological consequences of such an approach. As the threat from environmental weeds is becoming more fully recognized, an integrated, strategic and ecological approach to weed management is being recommended. In both countries, systems for screening new plants before allowing entry for cultivation have been developed. For already established plants, management is conducted within a legislative and policy framework such as the Regional Pest Management Strategies that operate through the Biosecurity Act 1993 in New Zealand. Noxious weed legislation in Australia has historically focused on agricultural weeds, but some Acts are (or have recently been) undergoing revision to give greater emphasis to environmental weeds and the involvement of the community in weed management. Quarantine, legislation, research and on‐ground management are complemented by education programmes about the impact and control of environmental weeds. This paper provides an overview of the ‘tool‐kit’ needed to manage environmental weeds in Australia and New Zealand, comparing and contrasting the approaches taken in the two countries. It also provides a broad framework for the case studies that make up this special issue on the ecology and management of environmental weeds in both countries.     

Wetland conservation and sustainable use under global change: a tropical Australian case study using magpie geese

Imminent shifts in environmental parameters due to climatic change might have profound ramifications for wetlands listed under the Ramsar convention. Although the exact mechanisms by which global change will affect these systems are not known, models that simulate component drivers, particularly at a broad spatial scale, can nevertheless allow for more informed conservation decision making. Such general inference is particularly needed for wetlands across the tropics, where less knowledge and fewer resources are available to mitigate the impacts on important conservation sites. Here we develop a case study of wetland loss to sea level rise across tropical north Australia (including Ramsar‐listed sites), and link these to a metapopulation model for a keystone endemic waterbird, the magpie goose Anseranas semipalmata. We projected published models on sea level rise through to the year 2400, and found a non‐linear trajectory of inundation up to 20 m above present levels. Digital elevation models were used to simulate sea level rise and the spatially differentiated loss of wetland habitat used by geese. Range retraction was linked to decline in ecological carrying capacity, and we coupled wetland‐specific habitat loss projections to a spatially explicit demographic metapopulation model. Additionally, we included alternate harvest strategies based on present‐day estimates of indigenous and non‐indigenous offtake of geese, and examined the synergy between wetland loss and hunting on extinction risk. Our results suggest that Australia's once‐abundant and widespread magpie goose will be reduced to a fragmented population of just a few thousand individuals within the next 200–300 yr. Harvest could continue for some time, up to a “tipping point” at around 5% loss of current wetland habitat, after which the decline of geese is rapid. Given the inexorable nature of sea level rise, short‐ to medium‐term conservation of waterbirds across Ramsar wetlands must prepare for adaptive wetland management, such as through buffer‐placement, and ongoing monitoring of harvest.     

Combining field experiments and predictive models to assess potential for increased plant diversity to climate‐proof intensive agriculture

Agricultural production systems face increasing threats from more frequent and extreme weather fluctuations associated with global climate change. While there is mounting evidence that increased plant community diversity can reduce the variability of ecosystem functions (such as primary productivity) in the face of environmental fluctuation, there has been little work testing whether this is true for intensively managed agricultural systems. Using statistical modeling techniques to fit environment–productivity relationships offers an efficient means of leveraging hard‐won experimental data to compare the potential variability of different mixtures across a wide range of environmental contexts. We used data from two multiyear field experiments to fit climate–soil–productivity models for two pasture mixtures under intensive grazing—one composed of two drought‐sensitive species (standard), and an eight‐species mixture including several drought‐resistant species (complex). We then used these models to undertake a scoping study estimating the mean and coefficient of variation (CV) of annual productivity for long‐term climate data covering all New Zealand on soils with low, medium, or high water‐holding capacity. Our results suggest that the complex mixture is likely to have consistently lower CV in productivity, irrespective of soil type or climate regime. Predicted differences in mean annual productivity between mixtures were strongly influenced by soil type and were closely linked to mean annual soil water availability across all soil types. Differences in the CV of productivity were only strongly related to interannual variance in water availability for the lowest water‐holding capacity soil. Our results show that there is considerable scope for mixtures including drought‐tolerant species to enhance certainty in intensive pastoral systems. This provides justification for investing resources in a large‐scale distributed experiment involving many sites under different environmental contexts to confirm these findings.