Farm land management app for complete farm land management, plan, rotate, project crops, monitor yield, compare current with historical yields, manage all farm activities and tasks, farm costs & budget management.
Conservation tillage (including no-till)
Of all agricultural land management activities suggested for GHG mitigation, conservation tillage has been the most widely applied9 and studied, with the majority of research investigating no-till (NT). Given the significance of NT in the literature and in practice, we will treat it as a separate activity in this synthesis and use the term “conservation tillage” more narrowly to denote any reduced-tillage practice other than NT. With over 280 field comparisons of soil C response to NT, the average mitigation potential for NT is estimated at 1.2 t CO2e ha− 1 yr− 1 (range of −0.2 to 3.2). With slight decreases in N2O and process emissions and no effect on CH4, the net GHG mitigation potential due to NT is 1.5 t CO2e ha− 1 yr− 1. Using data from 70 field comparisons, the soil C sequestration potential of other conservation tillage practices averages 0.4 t CO2e ha− 1 yr− 1 (range from − 0.5 to 1.4). Slight decreases in N2O and process emissions result in a net GHG mitigation potential of 0.7 t CO2e ha− 1 yr− 1.
Some form of conservation tillage is now applied on more than 40% of U.S. cropland, with 24–35% of cropland under NT management (CTIC, 2008; Horowitz et al., 2010). Therefore, conservatively estimated, the maximum area applicable for conservation tillage is 72 Mha10 and that for NT is 94 Mha. These are not additive, as land intended for other conservation tillage would no longer be available for NT. While field research data focuses almost exclusively on continuous NT, some of the area counted as NT in these surveys is not continuously NT, but only for 1 or 2 years in a row (Horowitz et al., 2010).11 Thus, shifting from intermittent NT to permanent or semipermanent NT may open up additional opportunities for mitigation.
Since European immigrants settled in North America, much land has been under continuous cultivation, leading to significant reductions in soil organic matter (SOM) levels with respect to those under native conditions.12 Current SOC levels for agricultural land are 22–36% lower than uncultivated land (Franzluebbers and Follett, 2005; VandenBygaart et al., 2003). With soil exposed to the elements, erosion by wind and water removed organic material, and with it, crop nutrients. Lower SOM can result in lower soil fertility, with declines in crop production and greater reliance on fertilizer.
Reducing tillage from the traditional moldboard plow (inversion of the soil profile) to some form of reduced tillage or NT has become important for erosion control, maintaining soil fertility, and improved crop health. Equipment and chemical development has also played a significant role, allowing seed placement without a prepared seedbed and weed control without soil disturbance. Conservation tillage can take various forms, ranging in levels of soil disturbance. In NT (also called zero-till) systems, crops are seeded directly into the previous season's stubble, with an implement cutting into the soil only enough to plant the seeds. Other conservation tillage practices include (1) ridge-till, where crop rows are planted on top of ridges that are scraped off for planting and rebuilt during the growing season; (2) strip-till, where only the seed row zone is disturbed (tilled); and (3) mulch-till, a form of reduced tillage with residue retained and spread out, but tillage performed just prior to planting.
Research and experience show that less soil disturbance not only controls soil erosion and improved soil quality but also decreases SOM decomposition rates. This has been demonstrated by a comparison of 13C signatures in SOC from NT and conventional sites (Six and Jastrow, 2006) and by the observation of soil C sequestration in many studies, reversing the trend initiated by the early agricultural settlers.
SOC dynamics and C sequestration potential can also vary by agricultural history, for example, disparate conventional tillage (CT) practices between regions (moldboard plow is common in some areas but not others) and the wide range of soil disturbance levels that can be classed as conservation tillage. Greater levels of soil disturbance tend to result in lower SOC levels over time and reducing tillage from full-inversion moldboard plow is likely to net a greater SOC sequestration response than where business as usual consists of chisel plowing or disc cultivating. Different SOC response to varying tillage intensity was also noted in a review by West and Post (2002), who concluded that conservation tillage other than NT yields very little consistent soil C sequestration (NT increased SOC by 1.6–2.6 t CO2e ha− 1 yr− 1). Clear definitions of practice and residue retention13 may explain why NT tends to exhibit more consistent potential for soil C sequestration (Six et al., 2004; West and Post, 2002).
However, some researchers have also questioned whether NT actually sequesters soil C and have proposed that the prevalence of shallow sample depths in much of the reported data tends to overstate soil C changes due to NT (Baker et al., 2007; Luo et al., 2010).14 These assertions have generated significant discussion among the scientific community. High SOC variability at depth contributes to low statistical significance, and larger differences or additional samples may be needed before detection is possible (Franzluebbers, 2010; Kravchenko and Robertson, 2010). Also, regional and soil characteristics need to be considered more carefully. For example, the five studies cited by Baker et al. (2007) for which assessment at greater depths indicated negative SOC response to NT were all from moist and cool areas of Eastern Canada (VandenBygaart et al., 2003), where lower yields and greater N2O emissions most often make NT unviable as a GHG-mitigating activity.
There is scarcely any true wilderness left in the EU, so the ways in which land is managed affects the quality of the environment as well as the character and social fabric of much of rural Europe.
The Common Agricultural Policy (CAP) continues to be a major driver of land use and management decisions. Other sectoral policies, such as those promoting renewable energy, protecting biodiversity and regulating water quality and usage have an important influence too.
IEEP seeks to inform and influence the development of the key EU policies that affect the sustainable use of rural land and to encourage the integration of environmental priorities into these policies.
We provide independent policy research, analysis and advice focussing on ways in which farming and forestry can help to protect Europe’s natural resources and the wide range of environmental goods and services which they support.
The greatest potential for NT to sequester soil C seems to be in subhumid regions (precipitation-to-potential evapotranspiration ratios of 1.1–1.4 mm mm− 1; such as in midwestern and southeastern United States). Average soil C sequestration rates for the Southeast are the highest, at 1.65 t CO2e ha− 1 yr− 1 (Franzluebbers, 2010), and other regions demonstrate average rates of up to 1.10 t CO2e ha− 1 yr− 1 (Johnson et al., 2005; Liebig et al., 2005b; Martens et al., 2005; Six et al., 2004). In cooler and wetter soils—for example, those in the Minnesota or Wisconsin—maximum C storage may instead be achieved with occasional (e.g., biennial) tillage (Venterea et al., 2006).
LAND MANAGEMENT APP
An extensive body of literature in the field of agro-ecology claims to show the positive effects that maintenance of ecosystem services can have on sustainably meeting future food demand, by making farms more productive and resilient, and contributing to better nutrition and livelihoods of farmers. In Africa alone, some research has estimated a two-fold yield increase if food producers capitalize on new and existing knowledge from science and technology. Site-specific strategies adopted with the aim of improving ecosystem services may incorporate principles of multifunctional agriculture, sustainable intensification and conservation agriculture. However, a coherent synthesis and review of the evidence of these claims is largely absent, and the quality of much of this literature is questionable. Moreover, inconsistent effects have commonly been reported, while empirical evidence to support assumed improvements is largely lacking.
Objectives
This systematic map is stimulated by an interest to (1) collate evidence on the effectiveness of on-farm conservation land management for preserving and enhancing ecosystem services in agricultural landscapes, by drawing together the currently fragmented and multidisciplinary literature base, and (2) geographically map what indicators have been used to assess on-farm conservation land management. For both questions, we will focus on 74 low-income and developing countries, where much of the world’s agricultural expansion is occurring, yet 80% of arable land is already used and croplands are yielding well below their potential.
Methods/Design
To this end, reviewers will systematically search bibliographic databases for peer-reviewed research from Web of Science, SCOPUS, AGRICOLA, AGRIS databases and CAB abstracts, and grey literature from Google Scholar, and 22 subject-specific or institutional websites. Boolean search operators will be used to create search strings where applicable. Ecosystem services included in the study are pollination services; pest-, carbon-, soil-, and water-regulation; nutrient cycling; medicinal and aromatic plants; fuel wood and cultural services. Outputs of the systematic map will include a database, technical report and an online interactive map, searchable by topic. The results of this map are expected to provide clarity about synergistic outcomes of conservation land management, which will help support local decision-making.
Background
Food production systems are threatened in the face of growing food demand, climate change and land cover changes [1]. Agriculture accounts for 70% of water withdrawals worldwide [2], one third of all available energy [3], 75% of all deforestation [4], 19-29% of global GHG emissions, and is the largest contributor of non-CO2 GHG emissions [5]. Declines in ecosystem health have consequences for agricultural production, such as soil salinization from over-irrigation and eutrophication of watercourses from fertilizer application. Forty percent of arable land worldwide is already degraded [6]. Moreover, these trends are increasing as agriculture intensifies and expands. For example, between 1961-2005 agricultural production doubled in Sub-Saharan Africa [7], and globally, was one of the main drivers of degradation of 65% of natural ecosystems [8]. In the last century, forest cover decreased from 170-100 million ha and every year, palm oil cultivation is responsible for c. 300 000 ha of forest cover loss [9]. In the next 25 years, food production and availability must increase by 50–70% to keep pace with the demands of a global population expected to reach 8-10 billion, income growth, and changing consumer preferences [6,10]. To address these challenges, recent international meetings have been convened, such as the UN Summit of 2014, where leaders from 20 governments and 30 organizations pledged their commitment to addressing food security through the formation of the Global Alliance for Climate-Smart Agriculture. Balancing the need to provide enough food for a growing population while maintaining healthy ecosystems and habitats is thus arguably one of the most pressing issues of the 21st century [1,6].
Ecosystem services as incentives for conservation agricultural land management
An emerging strategy being championed for conservation is the ecosystem service framework, which proponents consider more likely to be relevant to agricultural landscapes and their associated people than traditional biodiversity conservation [11,12]. The ecosystem services framework can be used to capture how human action both impacts and is affected by ecosystem responses to land use and land use changes [13].
Although various comprehensive frameworks and classifications refined and omitted categories [14,15], the framework for ecosystem services referred to is based on the Millennium Ecosystem Assessment (MA) [8], as this was the first large-scale ecosystem service assessment and categories are widely recognized [16]. This includes supporting services (e.g. carbon regulation, pest regulation, nutrient cycling), regulating services (e.g. water/soil regulation and supply, pollination services), provisioning services (e.g. fuel wood, medicinal and aromatic plants) and cultural services (e.g. education, recreational, spiritual, tourism, bequest or aesthetic value). Ecosystem goods and services are stocks or flows of materials that deliver welfare gains or losses that are material (e.g. fuel wood), as well as non-material (e.g. recreational services) [17]. Ecosystem elements are both biotic and abiotic and are generally described in terms of amounts (e.g. taxonomic, functional, chemical or physical units) [18-20]. Ecosystem processes, often used interchangeably with ecosystem functions, are the complex interactions (e.g. events, reactions or operations) among elements of ecosystems (e.g. events, reactions or operations), and are generally described in terms of rates [21].
Since the publication of the MA in 2005, the ecosystem services framework has gained traction - in terms of research, a spectrum of tools, and funding mechanisms [22,23]. Dedicated journals have been launched (e.g. International Journal of Biodiversity Science in 2005, Ecosystem Services and Management in 2005, Ecosystem Services in 2012), alongside graduate programs (e.g. MSc in Ecosystem Services, University of Edinburgh). Funding bodies are also prioritizing research into more comprehensive quantification of values of ecosystem services and the link with human health and wellbeing, such as the $65 m 7 year programme on Ecosystem Services and Poverty Alleviation (ESPA) and the $11 m + 6 year Valuing Nature programme led by the National Environment Research Council [24]. Moreover, ecosystem services projects attract on average more than four times as much funding as traditional biodiversity conservation projects, through greater corporate sponsorship and a wider variety of finance tools [11]. Supported by this research, there is a growing spectrum of ecosystem assessment tools, including computer-based platforms using national data (e.g. Integrated Valuation of Ecosystem Services and Trade-offs (InVEST), modelling and scenario driven tools (e.g. MIMES, ARIES), as well as efforts to integrate these frameworks (e.g. the Common International Classification on Ecosystem Services (CICES)). The ecosystem services framework has been used for international negotiation and collaboration in platforms, such as the Ecosystem Services Partnership in 2008, the International Panel on Biodiversity and Ecosystem Services in 2012, and the EU 2020 Biodiversity Strategy (e.g. Target 2) [1]. National governments have also incorporated ecosystem services frameworks to inform budget assignment and thematic planning prioritization, such as the UK’s National Ecosystem Service Assessment [17] and Foresight Report [1], that relates ecosystem services to agriculture and food security. The approach has further gained traction in the private sector, and has been used to conduct economic valuations in carbon (e.g. Voluntary Carbon Standard in South Africa), timber (e.g. Reduced Emissions from Deforestation and Degradation (REDD+) in Nigeria) and watersheds (e.g. Payments for Ecosystem Services in Costa Rica) [25].
The role of conservation land management in maintaining ecosystem services
Given the importance of ecosystem services to the sustainability and security of agricultural systems, as well as the current rate at which those services are being degraded by agricultural systems, a key need has arisen to implement ecosystem service conservation strategies on farms. A variety of alternative practices to conventional or intensive agriculture have been proposed, which we group under the term “conservation land management” for the purposes of this study. Conservation land management strategies preserve or enhance ecosystem services without compromising farm production and may be adopted before, during or after cultivation [26]. Strategies may be active, such as surface crop residue management, or passive, such as the existence of native vegetative patches in fields. Practices may incorporate principles, amongst others, of multifunctional agriculture (producing food and non-food commodities, maintaining wild crop varieties, traditional landraces and local culture [27]), sustainable intensification (relieving pressure on land expansion and limiting forest encroachment [7]), and conservation agriculture (practices of no-tillage, permanent soil cover using crop residues or cover crops, and crop rotation [28]). Such practices often require minimal inputs with opportunities for enhancing small-holder production [26]. Farm land management app for complete farm land management, plan, rotate, project crops, monitor yield, compare current with historical yields, manage all farm activities and tasks, farm costs & budget management.
Specific examples of conservation land management strategies include growing leguminous cover crops to fix nitrogen, retain moisture, stimulate root-growth and encourage below-ground microbial activity [29]; no till or minimum till systems and crop rotation, to influence soil organic carbon sequestration [26,30] and yield [26]; mosaic or matrix management of natural vegetation within or adjacent to farmland (e.g. set aside areas, buffer strips, hedgerows or field margins), to encourage the presence of beneficial wild pollinator populations [31]; fallowing to suppress leaching and erosion of organic matter and nutrients, and increase soil cation exchange [32]; intercropping and the use of push-pull systems to regulate detrimental pest populations and enhance natural enemy populations [33]; water conservation techniques, such as drip irrigation, alternative wet and dry irrigation, raised beds, tied ridges and ditches, and growing grass filter strips, to influence water regulation and supply and control erosion [34,35]; and the intercropping of timber trees with shade tolerant crops, or multi-story cropping, to reduce the presence of weeds and promote nutrient cycling [27]. To conceptualize a theory of change, Figure 1 shows examples of conservation land management strategies (single programs or comprehensive community initiatives) (red) that may bring about outcomes on supporting or provisioning ecosystem services (blue), through key measurable indicators or proxies (black).
Illustrative theory of how conservation land management strategies may bring about change in ecosystem service provision. [Red] indicates conservation land management strategies; [Black] indicators; [Blue] ecosystem services; [+] indicates an increase; [-] indicates a decrease; thick solid lines are estimated relations referenced in the text; while dotted lines are proxies for ecosystem services. The box surrounding the figure indicates that all factors influence crop productivity.
The figure illustrates the complex web of activity that is required to bring about change, while assumptions indicated in the flow arrows are not exclusive or exhaustive, and require varying degrees of research verification. We still lack a coherent evidence base showing how effectively these management strategies preserve or enhance ecosystem services overall.
Synthesizing evidence is complex for three main reasons. Firstly, change in conservation land management may affect various ecosystem services differently. For example, some studies report that long-term no-till can improve soil fertility, recovery and decrease erosion, but no-till can also lead to soil compaction, limit water infiltration and can hinder seed germination [36,37]. Other studies have reported that managing runoff can increase and stabilize crop production and deposit plant nutrients in soil, but runoff can adversely affect nutrient cycling [38]. The management of ecosystem services therefore requires making judgements about trade-offs, not least, the trade-off between agricultural production and environmental protection [23]. Secondly, impacts of land management on ecosystem services are often quantified by indicators or proxies of ecosystem processes, thought to subsequently impact ecosystem services. However, evidence for the adequacy of these proxies is often incomplete or inconsistently reported. For example, many studies suggest higher biodiversity allows for higher levels of ecosystem service provision [39], while others argue there is little hard evidence to show the necessity of a diversity of natural enemies in regulating pests on farms [40]. Thirdly, much of the evidence is spread across different disciplinary “silos”, with very limited synthesis. Some studies also overstate the benefits of land management strategies [37].
Land managers, and other parties interested in ecosystem services, would benefit from much greater clarity and information on the effectiveness of conservation land management strategies, in order to decide which management strategies to implement at the farm level. When evidence is so extensive and disparate, a rapid first step in such an informational synthesis is a systematic map, a rigorous methodological tool of data extraction of peer-reviewed and grey literature [41]. Systematic maps have the same precision as a review, while no evidence synthesis is attempted and a critical appraisal of the quality of evidence is limited in depth [42,43]. Previous attempts to synthesize this body of research have focused on particular regions, such as Africa [44,45], a limited set of practices [28], or have evaluated management outcomes purely in terms of crop responses [45]. Our systematic map will build on this research, both geographically, and in terms of the management strategies and ecosystem services studied.
Against this background, the aim of this systematic map is to review the state of evidence that reports on the effectiveness of on-farm conservation land management for protecting or enhancing ecosystem services. First, we aim to provide a better summary of different strategies proposed and tested, in which crops, habitats and regions, and over what timeframes. Secondly, we will identify the pathways by which practices are assumed to influence ecosystem service provision by reporting on measurable indicators assessed in studies. We will differentiate between methodologies that are experimental, quasi-experimental and non-experimental and indicators that are physical, chemical, biological, social and/or economic. The spatial scale of the study is at the field level, as this is the scale at which most decisions for land management are made and need to be informed [46]. Our geographical coverage will be developing regions, as this is where much of agricultural expansion is occurring [1], yet 80% of arable land is already used [47] and croplands are yielding well below their potential [4]. In some cases, developing regions may also depend on ecosystem services rather than technological inputs to support agriculture, due to lower financial, technical and credit-borrowing capacity.
Objectives of the systematic map
1.
Collate studies providing evidence on the effectiveness of on-farm conservation land management practices on ecosystem service provision in agricultural landscapes in low-income and developing countries.
2.
Geographically map which indicators have been used for on-farm assessments of conservation land management in low-income and developing countries.
3.
Produce an online interactive map, searchable by topic.
Elements of the systematic map question
Population: Farms in low/middle income and developing countries.
Intervention: Conservation land management strategies adopted to support productive agriculture, while simultaneously preserving or enhancing ecosystem services.
Comparators: Farms without conservation land management strategies, conventional/intensive agriculture or natural sites.
Outcomes: Measured changes in ecosystem services, including supporting services (e.g. carbon regulation, pest regulation, nutrient cycling), regulating services (e.g. water/soil regulation and supply, pollination services), provisioning services (e.g. fuel wood, medicinal and aromatic plants) and cultural services (e.g. education, recreational, spiritual, tourism, bequest or aesthetic value).
Method
Search strategy
The following search strategy and research question have been developed with stakeholders in two meetings in South Africa (February 2014) and UK (June 2014). Expertise of stakeholders span the fields of environment, conservation, biodiversity, development, agriculture, entomology, soil science, pollination, anthropology and ecology. Further comments on earlier drafts of this protocol were provided after the workshops and over email with other contributors (Additional file 1).
Language
The systematic map will be limited to studies published in English. This decision was made as the larger body of literature is in English, as well as this being the linguistic competency of the review team and also provides a mechanism for restricting the scale of the study [41,48]. Should a full systematic review be conducted arising from the map, French, Spanish or Portuguese would be considered to cover literature from regions in Africa, South East Asia and Latin America. Future assessments will create language-specific search strings associated with the research question.
Key search terms
A list of key terms, searched at levels of title, and abstract level is listed in Additional file 2. Each of the terms relate to the components of the research question and PICO (Population Intervention Comparator Outcome). The list was compiled by experts from invited institutes and universities, who met at the two stakeholder workshops. Terms were built into strings, used in preliminary scoping searches conducted in the Web of Science (WOS) CAB Abstracts, and Google Scholar. In WOS 27 search strings were tested, with the final string resulting in 7558 hits. The search strategy contains synonyms and near-synonyms, and does not make a distinction between definitions used in the primary literature. We will use these strings as the basis of the search, however an iterative approach to identifying search terms will be adopted to improve the strategy and help minimize bias. Details of the search logic and the development of the final strings are found in Additional file 3. Boolean search operators will be used to connect search terms in the usual way and subject to the specific rules of individual databases. In the search wildcards will be used with care and will vary slightly from database to database. Such variations between search strategies in each database and source will be documented and reported in the final map. The date of the search will be documented, allowing for updating of future mapping.
Farm land management app for complete farm land management, plan, rotate, project crops, monitor yield, compare current with historical yields, manage all farm activities and tasks, farm costs & budget management.