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Grazing and ecosystem service delivery in global drylands
Abstract
Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and speciespoor drylands, whereas positive effects of grazing were observed in colder and species-rich areas.
Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure.
... For instance, plant functional and taxonomic diversities may vary independently of each other in response to grazing (Köbel et al., 2021) and the interaction between grazing and precipitation (De Bello et al., 2006), with outcomes highly dependent on local environmental constraints (Chillo et al., 2017) and type of ecosystem (Plexida et al., 2018;Carvalho et al., 2020), as well as on climatic and historical contexts (Díaz et al., 2007). Indeed, the effects of grazing and precipitation on biodiversity and ecosystem properties can vary from positive to negative depending on local conditions (Li et al., 2018;Maestre et al., 2022). Importantly though, the introduction of grazing is generally known to favour certain life strategies and result in changes to plant functional composition in a variety of ecosystems globally (Díaz et al., 2007), including the montado (Castro et al., 2010), where grazing has been a common land management practice for centuries (see below). ...
... This seems to be the case at our study sites, where we found a negative relationship between cattle grazing and SOC. Yet, previous studies have reported positive, neutral or negative effects of grazing on SOC, indicating effects are highly context-specific and may depend on the interaction between grazing and several other factors, including precipitation and soil (fine textured vs. sandy soils) and vegetation type (McSherry and Ritchie, 2013;Maestre et al., 2022). Positive effects of grazing on SOC have been reported from sites with a mean annual precipitation of 600 mm or less, with a negative effect reported above that threshold, potentially as a result of lower initial SOC pools and greater root-to-soil C ratios in semiarid environments compared to more mesic environments, as well as higher (and more active) microbial biomass C and greater pools of labile organic matter leading to higher C turnover rates under grazing in relatively wet sites (Derner and Schuman, 2007;Piñeiro et al., 2010). ...
... Positive effects of grazing on SOC have been reported from sites with a mean annual precipitation of 600 mm or less, with a negative effect reported above that threshold, potentially as a result of lower initial SOC pools and greater root-to-soil C ratios in semiarid environments compared to more mesic environments, as well as higher (and more active) microbial biomass C and greater pools of labile organic matter leading to higher C turnover rates under grazing in relatively wet sites (Derner and Schuman, 2007;Piñeiro et al., 2010). Contrarily, studies conducted in central Asia found negative effects of grazing on SOC at sites with less than 600 mm of mean annual precipitation (Pei et al., 2008), while a global study on drylands found decreased soil carbon stocks and increased soil erosion under warmer climates and higher grazing intensities, though positive effects were reported from colder drylands (Maestre et al., 2022). Negative effects of grazing have been attributed to a decrease in vegetation cover and an increase in soil erosion associated with continuous grazing leading to poaching (Pei et al., 2008;Golluscio et al., 2009). ...
A R T I C L E I N F O Keywords: Agro-silvo-pastoral systems dehesa Drylands Mediterranean savannahs montado Open woodlands Plant functional traits RLQ analysis A B S T R A C T Mediterranean oak-dominated agro-silvo-pastoral systems of southwestern Europe (called montado in Portugal and dehesa in Spain) are semi-natural, savannah-style High Nature Value farmlands (HNVfs) shaped by centuries of anthropogenic (e.g., cultivation, grazing) and natural (e.g., drought) disturbances. Therefore, changes in grazing and precipitation may alter their vegetation composition and ecosystem properties and impact upon their long-term viability. We quantified the responses of soil organic carbon (SOC) and plant taxonomic and functional trait diversities to cattle grazing and inter-annual changes in precipitation across three open-woodland sites within the montado landscape in Alentejo, southern Portugal. The sites are characterised by the presence or absence of cattle grazing and different amounts of mean annual precipitation (ranging from semiarid to dry subhumid). Three different precipitation periods were used: a shorter autumn-to-spring period and longer 12-and 18-month periods before sampling. Specific leaf area, plant height and seed mass were used to estimate single-trait community weighted means and a multi-trait measure of community functional diversity (Rao's Q). SOC and plant species richness responded negatively to the presence of cattle grazing but positively to increase in precipitation (and its interaction with cattle grazing), while trait-based measures were largely unresponsive to cattle grazing and precipitation (though RLQ analysis revealed strong controls of the environmental variables on plant life cycle, growth form, leaf phenology and dispersal strategies). SOC was most responsive to longer-term (18-month) changes in precipitation, whereas plant species richness was most responsive to shorter-term (autumn-to-spring) changes in precipitation. These results suggest that different components of plant diversity respond differently to external drivers in montado HNVfs, while the response time of soil properties may be longer than that of plant taxonomic diversity.
... Maestre et al. (1) analyse the effect of livestock grazing on drylands at the global scale, contrasting low, medium, and high levels of grazing pressure. Their effort in putting together an extensive collection of sampling points in many of the world's grazing ecosystems, and measuring multiple environmental variables is commendable, with a very detailed capture of environmental services. ...
... Mobility is a core strategy that both domestic and wild herbivores use to respond to environmental variability, but this factor is excluded from the study by Maestre et al. (1), in which only xed plots with assumed constant grazing pressure are assessed. In sedentary livestock systems, productivity (3), climate change mitigation (4), tree regeneration (5), and genetic health of plant populations (6) underperform compared to mobile livestock systems in the same environment. ...
... Migratory use of the drylands can accommodate a large biomass of both domestic and wild herbivores (10). Maestre et al. (1) observe a correlation between low wild herbivore diversity and higher grazing pressure in drier areas. This may, however, not re ect causality but rather the need for wild herbivores to migrate seasonally away from drier areas, or may re ect poor governance of rangelands that impedes domestic or wild herbivore migration in the areas that need it most. ...
Maestre et al. (Reports, 24 November 2022, p. 915) analyze livestock grazing in global drylands without adequately considering critical ecological, social, and economic variables. Their analysis ignores mobile pastoralism practices and land governance arrangements, critical for sustainable grazing in dry rangelands.
... In North America, the demand for dryland ecosystem services likely exceeds the current supply, making conservation and careful management of the large dryland area within the DoD land estate crucial for providing and safeguarding ecosystem services (Bengtsson et al., 2019). Drylands that are warmer and have lower species diversity are particularly vulnerable to reductions in services due to increased disturbance, and biodiversity loss in drylands can further exacerbate the decline in ecosystem services when coupled with disturbances and land use pressures (Maestre et al., 2022). The climate-biodiversity status of DoD lands creates widespread management challenges for military training areas in drylands where the primary land use can be destructive (Warren et al., 2007;Zentelis et al., 2017). ...
... The phenomenon is so pronounced that it has led previous researchers to posit the "heterogeneous disturbance hypothesis" and argue that the disturbance regimes of these DoD drylands have illuminated ecological principles (Warren et al., 2007), and there are examples of specific positive effects of military activities on species across ecosystems (Aycrigg et al., 2015;Dvoř akov a et al., 2023;Warren & Büttner, 2008;Zentelis & Lindenmayer, 2015). Despite unique management history, the magnitude and type of ecosystem services from the DoD land base are primarily controlled by the biophysical constraints of terrestrial ecosystems: average and extremes in climate, geologic history, biogeographic influences, and other controls (Maestre et al., 2022). Understanding the primacy of these controls helps contextualize the type and magnitude of ecosystem services supplied by a given location given its management history. ...
Lands devoted to military use are globally important for the production of ecosystem services and for the conservation of biodiversity. The United States has one of the largest military land estates in the world, and most of these areas occur in water‐limited landscapes. Despite many of these areas receiving intense or sustained disturbance from military training activities, the structure and function of ecosystems contained within their boundaries continue to provide critical benefits to people across spatial scales. The land owned and managed by the Department of Defense is subject to regulation across local, state, and federal governing bodies, constraining and shaping both how land management is conducted and how ecosystem services are prioritized. Here, we explored the supply of ecosystem services from military lands in dryland areas of the United States using key indicators of ecosystem services: biodiversity estimates derived from range maps, ecosystem productivity estimates from satellite observations, and spatially explicit, hierarchical ecosystem classifications. Additionally, we utilized content analysis of the environmental management plans of these areas to describe the unique set of demands and regulatory constraints on these areas. We found that the US military land estate in drylands contains many types of ecosystems and provides a large and diverse supply of ecosystem services, comparable to the sum of services from public lands in these areas. Additionally, the degree to which the ecosystem services concept is captured in environmental management plans is strongly shaped by the language of the governing legislation that mandated the use of environmental management plans in these areas, although these plans do not explicitly address land management using the concept of ecosystem services. Collectively, our findings suggest that military use and management of land represents an important source of ecosystem services, that military land use can be considered a cultural ecosystem service unto itself, and that top‐down regulation can affect how these services are identified and valued. Our work highlights the need for the research and conservation communities to quantify ecosystem services from individual military installations so that both services and biodiversity can be safeguarded in an era of military conflict across the globe.
... An experimental study in the Great Plains (USA) showed that, at the plot level (10 m 2 ), under bison grazing native species richness was 103% higher and under cattle grazing 41% higher when compared to ungrazed plots (Ratajczak et al. 2022). Furthermore, using a standardised survey at 98 sites across six continents, Maestre et al. (2022) found that in drylands, increasing grazing pressure shifts the relationships between plant species richness and aboveground biomass from negative to positive at the plot level (45 × 45 m). The effects of grazing on biodiversity, however, remain context-dependent as the results of the interactions between grazing pressure and abiotic and biotic features cause some uncertainty on the effects of grazing on ecosystem services and nature's contributions to people (Maestre et al. 2022). ...
... Furthermore, using a standardised survey at 98 sites across six continents, Maestre et al. (2022) found that in drylands, increasing grazing pressure shifts the relationships between plant species richness and aboveground biomass from negative to positive at the plot level (45 × 45 m). The effects of grazing on biodiversity, however, remain context-dependent as the results of the interactions between grazing pressure and abiotic and biotic features cause some uncertainty on the effects of grazing on ecosystem services and nature's contributions to people (Maestre et al. 2022). Furthermore, at the plot level, we found a positive association between mowing and fertilising intensity and biomass production, while grazing was positively associated with plant diversity in protected areas. ...
Context
A key global challenge is to meet both the growing demand for food and feed while maintaining biodiversity’s supporting functions. Protected grasslands, such as Natura 2000 sites in Europe, may play an important role in harmonising productivity and biodiversity goals. This work contributes to an understanding of the relationship between forage production and plant diversity in protected and non-protected grasslands.
Objectives
We aimed to identify differences in plant diversity and forage production between protected and non-protected grasslands by assessing the effects of land-use intensity (i.e. mowing, grazing, fertilising) on these variables.
Methods
Data were available for 95 managed grassland plots (50 × 50 m) in real-managed landscapes. After controlling for site conditions in the analysis, we tested for significant differences between protected and non-protected grasslands and used a multi-group structural equation modelling (SEM) framework to investigate the linkages between land-use intensity, biomass and plant diversity.
Results
In protected grasslands, plant diversity was significantly higher while forage production was significantly lower. In non-protected grasslands we found significantly higher land-use intensity, particularly in relation to mowing and fertilisation. Grazing intensity did not significantly differ between protected and non-protected grasslands. In non-protected grasslands we found a significant negative association between forage production and plant diversity. However, this effect was not significant in protected grasslands. We also found a negative association between land-use and plant diversity in both grassland types that was related to mowing and fertilising intensity. These two management aspects also influenced the positive association between land-use intensity and forage production. Furthermore, environmental conditions had a positive effect on forage production and a negative effect on plant diversity in protected grasslands.
Conclusions
Our results confirm that the protection of grassland sites is successful in achieving higher plant diversity compared to non-protected grasslands and that protected grasslands do not necessarily trade-off with forage production. This is possible under moderate grazing intensities as higher land-use intensity has a negative effect on plant diversity, particularly on rare species. However, forage production is lower in protected sites as it is driven by mowing and fertilisation intensity. Future research needs to further investigate if the nature of these relationships depends on the livestock type or other management practices.
... Aridity had a predominantly negative effect on ecosystem structure and functioning across China's drylands, whereas the effects of grazing ranged from weaker negative to positive or neutral, depending on the Managed livestock grazing, which occurs in ~65% of global drylands 20 , may affect plant community composition and ecosystem functioning in a similar way as aridity 20 . Drivers of ecosystem structure and functioning in drylands, such as climatic conditions and grazing pressure, rarely act independently, and interactions among them may act synergistically or in opposition [21][22][23][24] . However, very few studies have considered the potential interactions between aridity and grazing and the joint effects on the response of ecosystem variables 20,22,25 , and none has evaluated whether and how they jointly shape ecological thresholds in drylands. ...
... pressure, could be an effective measure to reduce the risk of land degradation and desertification in these areas. However, keeping a moderate and optimal grazing pressure by increasing livestock by 92 ± 37 units per square kilometre in wetter environments (22.3% of drylands) is key to enable production of meat, milk and leather, thereby supporting local livelihoods, and to enhance species richness and both ecosystem multifunctionality 36 and ecosystem services 24 . In addition, rangeland management activities should aim, whenever possible, to enhance plant species richness to alleviate the negative effects of ongoing increases in temperature being experienced in many Chinese drylands. ...
Degradation of ecosystems can occur when certain ecological thresholds are passed below which ecosystem responses remain within ‘safe ecological limits’. Ecosystems such as drylands are sensitive to both aridification and grazing, but the combined effects of such factors on the emergence of ecological thresholds beyond which ecosystem degradation occurs has yet to be quantitatively evaluated. This limits our understanding on ‘safe operating spaces’ for grazing, the main land use in drylands worldwide. Here we assessed how 20 structural and functional ecosystem attributes respond to joint changes in aridity and grazing pressure across China´s drylands. Gradual increases in aridity resulted in abrupt decreases in productivity, soil fertility and plant richness. Rising grazing pressures lowered such aridity thresholds for most ecosystem variables, thus showing how ecological thresholds can be amplified by the joint effects of these two factors. We found that 44.4% of China’s drylands are unsuitable for grazing due to climate change-induced aridification, a percentage that may increase to 50.8% by 2100. Of current dryland grazing areas, 8.9% exceeded their maximum allowable grazing pressure. Our findings provide important insights into the relationship between aridity and optimal grazing pressure and identify safe operating spaces for grazing across China’s drylands.
... The importance of nutrient-poor soils for these endangered grassland ecosystems is mirrored in restoration approaches that actively reduce soil fertility (Fig. 1b), sometimes involving the complete removal of the fertile topsoil (Kiehl et al., 2010). This restoration approach strongly contrasts the large global extent of heavily degraded grassland and rangeland soils (Bai and Cotrufo, 2022;Maestre et al., 2022). In addition, reducing soil fertility can also be desirable when managing invasive species or as a consequence of changing from resourceintensive irrigated agriculture to more sustainable dryland agriculture (Sims et al., 2020). ...
... Grasslands and rangelands provide many important ecosystem services, of which food production represents only one (Maestre et al., 2022;Schils et al., 2022). A recently introduced indicator to assess ecosystem degradation is the number of ecosystem services simultaneously provided, i.e., ecosystem multifunctionality. ...
Restoring degraded ecosystems is crucial for human wellbeing and biodiversity conservation. Nowadays, ecological restoration goes far beyond recovering a degraded ecosystem according to a historic reference. Instead, more specific restoration goals are set, following global environmental strategies that are individually highly important, but often conflicting. Furthermore, various pitfalls exist regarding the evaluation of ecosystem degradation and, directly related to this, the question what is the most desirable ecological state of an ecosystem. Ignoring such issues can lead to a failure of restoration projects and do more ecological (and social) harm than good. A crucial aspect in tackling conflicting goals and circumnavigating restoration pitfalls is the considerate choice of the indicators to assess ecosystem degradation and restoration capacity.In this Perspective, grasslands and rangelands are used exemplarily for ecosystems with globally high restoration demand. I discuss potential restoration pitfalls related to enhancing carbon sequestration, soil fertility, and ecosystem service multifunctionality. For all three goals, strong trade-offs and unwanted side effects exist. For example, while increasing carbon storage and restoring soil fertility are widely acknowledged environmental goals, both can compromise other restoration targets such as grassland biodiversity and further ecosystem services, depending on the specific context. Thus, there are no universally applicable indicators for ecosystem degradation and restoration. Instead, indicator systems have to account not only for strong trade-offs among restoration goals but also for a number of environmental and socio-ecological misconceptions, such as presented for the case of grassland ecosystems.I argue that one-sided goal setting and an imprudent choice of indicators can misguide the science-policy dialogue and related restoration efforts. To avoid this, restoration programs must integrate holistic assessments of their objectives across spatial scales and with all stakeholders concerned. The associated ecological indicator system for restoration success and program performance must therefore also be based on multidisciplinary and participatory approaches. Restoration and degradation indicators have to further ensure the target ecosystem is correctly and comprehensively identified, and the manifold conflicting land management objectives associated with heterogeneous human societies are taken into account. Researchers can assist this process by by-default considering the socio-ecological context of a restoration target and by identifying trade-offs arising from potential solutions, before these are suggested to the public. Only when all these aspects are considered, restoration projects at the local to global scale will result in long-term sustainable outcomes.
... Systems with low plant diversity may be especially sensitive to large grazers, particularly when combined with other stressors such as invasive species or climatic extremes because other plant species are not present to replace those targeted by grazers (Biggs et al., 2020). While there is growing understanding of context-dependent effects of large grazers on terrestrial systems (Maestre et al., 2022), progress in coastal wetlands such as saltmarshes has been hampered by a geographic bias in study effort and an emphasis on farmed rather than wild or semi-wild grazers (Davidson et al., 2017). ...
Large grazers modify vegetated ecosystems and are increasingly viewed as keystone species in trophic rewilding schemes. Yet, as their ecosystem influences are context‐dependent, a crucial challenge is identifying where grazers sustain, versus undermine, important ecosystem properties and their resilience.
Previous work in diverse European saltmarshes found that, despite changing plant and invertebrate community structure, grazers do not suppress below‐ground properties, including soil organic carbon (SOC). We hypothesised that, in contrast, eastern US saltmarshes would be sensitive to large grazers as extensive areas are dominated by a single grass, Spartina alterniflora. We predicted that grazers would reduce above‐ and below‐ground Spartina biomass, suppress invertebrate densities, shift soil texture and ultimately reduce SOC concentration.
We tested our hypotheses using a replicated 51‐month large grazer (horse) exclusion experiment in Georgia, coupled with observations of 14 long‐term grazed sites, spanning ~1000 km of the eastern US coast.
Grazer exclusion quickly led to increased Spartina height, cover and flowering, and increased snail density. Changes in vegetation structure were reflected in modified soil texture (reduced sand, increased clay) and elevated root biomass, yet we found no response of SOC. Large grazer exclusion also reduced drought‐associated vegetation die‐off.
We also observed vegetation shifts in sites along the eastern US seaboard where grazing has occurred for hundreds of years. Unlike in the exclusion experiment, long‐term grazing was associated with reduced SOC. A structural equation model implicated grazing by revealing reduced stem height as a key driver of reduced soil organic carbon.
Synthesis: These results illustrate the context dependency of large grazer impacts on ecosystem properties in coastal wetlands. In contrast to well‐studied European marshes, eastern US marshes are dominated and structured by a single foundational grass species resulting in vegetation and soil properties being more sensitive to grazing. Coastal systems characterised by a single foundation species might be inherently vulnerable to large grazers and lack resilience in the face of other disturbances, underlining that frameworks to explain and predict large grazer impacts must account for geographic variation in ecosystem structure.
... Our study found that temporal stability and its components of ecosystem multifunctionality on the Mongolian Plateau had consistent negative responses to livestock grazing, but inconsistent responses to resource addition. In accordance with most previous studies (Maestre et al., 2022;Qin et al., 2019;Wang et al., 2020), our findings showed that livestock grazing, especially moderate F I G U R E 4 Piecewise SEM of effects of multiple environmental changes on temporal stability, mean, and SD of total multifunctionality (a), aboveground (b) and belowground multifunctionality (c) via soil abiotic variables, species diversity, and temporal asynchrony of plant and soil biota in the experiment with multiple environmental changes. Due to the lack of interaction among variables in soil abiotic variables, species diversity, and temporal asynchrony of plant and soil biota, we group them in the same box in the model for graphical simplicity. ...
The role of plant biodiversity in stabilizing ecosystem multifunctionality has been extensively studied; however, the impact of soil biota biodiversity on ecosystem multifunctional stability, particularly under multiple environmental changes, remains unexplored. By conducting an experiment with environmental changes (adding water and nitrogen to a long‐term grazing experiment) and an experiment without environmental changes (an undisturbed site) in semi‐arid grasslands, our research revealed that environmental changes‐induced changes in temporal stability of both above‐ and belowground multifunctionality were mainly impacted by plant and soil biota asynchrony, rather than by species diversity. Furthermore, changes in temporal stability of above‐ and belowground multifunctionality, under both experiments with and without environmental changes, were mainly associated with plant and soil biota asynchrony, respectively, suggesting that the temporal asynchrony of plant and soil biota has independent and non‐substitutable effects on multifunctional stability. Our findings emphasize the importance of considering both above‐ and belowground biodiversity or functions when evaluating the stabilizing effects of biodiversity on ecosystem functions.
... Similarly, within the Arizona desert (North America), shoot and root biomass as well as SOC and SIC pools remained largely unaffected by grazing, with climatic conditions playing a predominant role in determining their concentrations (McKenna et al., 2022). In arid polyphytic grasslands, the timing of animal grazing significantly influences biomass accumulation and the prevalence of different plant species (Maestre et al., 2022). For instance, within the Chihuahua desert, grazing during summer resulted in lower biomass accumulation compared to grazing during winter or fall, even during wetter-than-average years (Lasch e et al., 2023). ...
Deserts represent key carbon reservoirs, yet as these systems are threatened this has implications for biodiversity and climate change. This review focuses on how these changes affect desert ecosystems, particularly plant root systems and their impact on carbon and mineral nutrient stocks. Desert plants have diverse root architectures shaped by water acquisition strategies, affecting plant biomass and overall carbon and nutrient stocks. Climate change can disrupt desert plant communities, with droughts impacting both shallow and deep‐rooted plants as groundwater levels fluctuate. Vegetation management practices, like grazing, significantly influence plant communities, soil composition, root microorganisms, biomass, and nutrient stocks. Shallow‐rooted plants are particularly susceptible to climate change and human interference. To safeguard desert ecosystems, understanding root architecture and deep soil layers is crucial. Implementing strategic management practices such as reducing grazing pressure, maintaining moderate harvesting levels, and adopting moderate fertilization can help preserve plant–soil systems. Employing socio‐ecological approaches for community restoration enhances carbon and nutrient retention, limits desert expansion, and reduces CO2 emissions. This review underscores the importance of investigating belowground plant processes and their role in shaping desert landscapes, emphasizing the urgent need for a comprehensive understanding of desert ecosystems.
... Similarly, the millennia-long decline of large-bodied mammals is recently punctuated by a spasm of extirpations, which sharply transform local disturbance regimes (Pringle et al., 2023;Ripple et al., 2015;Smith et al., 2018). The impacts of shifting disturbance regimes may be especially acute in drylands, which cover over 40% of global land area and are often sensitive to even small changes in bottom-up (precipitation) or top-down (herbivory) forces (Maestre et al., 2016(Maestre et al., , 2022. ...
Climate models predict increases in the frequency and intensity of extreme-weather events. The impacts of these events may be modulated by biotic agents in unpredictable ways, yet few experiments cover sufficient spatiotemporal scales to measure the interactive effects of multiple extreme events. We used a 28-year experiment spanning several significant droughts to investigate how rainfall, large herbivores, and soil-engineering termites affect understory vegetation in a semi-arid savanna. Herbivory was the dominant influence on community structure – decreasing cover, increasing species richness, and favouring occurrence of annuals more than perennials – but these effects were contingent on rainfall and termitaria in non-additive (hence unpredictable) ways that contrasted with expectations from previous work. A separate experiment affirmed that resource supplementation does not straightforwardly compensate for herbivory effects. Our study highlights the potency of top-down forcing in African savannas, suggests impressive robustness to drought, and underscores the value of multi-decadal experiments for disentangling multi-disturbance interactions.
... If our global data support this pattern, they would provide evidence for the relevance and accuracy of the mechanisms proposed by Holdo & Nippert. Also, testing this pattern in rangelands with varying grazing pressures, which are largely driven by domestic livestock (Maestre et al., 2022b), allows us to infer the presence and importance of disturbance-based mechanisms. ...
... Because global temperature is expected to increase in the coming years (Tebaldi and Knutti 2010), the combined changes in climate and land uses can affect landscape functioning and grasslands ecosystem services (Maestre et al. 2022) which can increase uncertainty as to whether the vegetation will persist in its original regime or shift to new community composition and functioning (Kaarlejärvi et al. 2015). Hence, we need to deepen our knowledge on reconstructing ecosystem responses to climate under different conditions of predominant grazing interactions (domestic or wild herbivores) and at large spatial and temporal scales. ...
The abandonment of traditional practices has transformed agro-pastoral systems, leading to a more frequent occurrence of passive rewilding of Mediterranean landscapes. Reconstructing ecosystem responses to climate under different grazing conditions (i.e., wild, and domestic ungulates) is important to understand the future of these ecosystems.
Here we study the different roles of domestic and wild herbivory in defining the climate-vegetation interaction. Specifically, we evaluated (1) the effect of climate on primary productivity at the landscape scale and (2) the long-term trends of vegetation biomass in response to passive rewilding or maintenance of traditional grazing systems.
This study was carried out in South-eastern Spain. We used satellite images to generate NDVI time series that proxy primary productivity and vegetation biomass. We combined the NDVI and climate data from two key landscapes: one with wild ungulates and another predominantly with domestic ungulates.
We detected a secondary succession process in areas with only wild ungulates. In domestic herbivory areas, vegetation biomass remained constant throughout time (30 years). In domestic herbivory areas temperature and seasonal precipitation affected primary productivity. In areas with only wild herbivory, primary productivity was mainly driven by annual precipitation, and it was less dependent on seasonal precipitation.
These results highlight the distinctive roles of herbivores in defining Mediterranean landscapes' adaptability to climate, through passive rewilding or traditional livestock use. Maintaining both ecosystems can enhance landscape heterogeneity and ecological sustainability in a context of climatic changes.
... Grasslands cover ~40% of the Earth's land surface, serving as a huge global reservoir of food, water, carbon, and biodiversity (Suttie et al., 2005;Buisson et al., 2022). Grazing by different herbivores (e.g., cattle, sheep) is pervasive across grasslands worldwide and plays a keystone role in regulating the structure and functioning of grassland ecosystems through multiple ways, such as defoliation, trampling, and excretion (Esmaeili et al., 2021;Maestre et al., 2022). Moreover, ungulates of different species exhibit various foraging behaviors: small or medium-sized ruminants (i.e., sheep) prefer plants with rich nutrients (i. ...
... There are both winners and losers from the changes that occur in abandoned areas, ultimately altering species assemblages across all taxa (Russo, 2007). Notwithstanding, the effects of grazing on ecosystem structure and functioning are still relatively unknown, as they strongly rely on local contexts (Maestre et al., 2022). Besides, most of the field studies have focused on presence-absence grazing designs, while studies analysing actual grazing gradients are scarce in the literature (Eldridge et al., 2016). ...
... Regional experiments are needed to determine whether domestic herbivore impact on biodiversity and ecosystem functions is general or whether these effects depend on grassland aridity conditions. Second, current work exploring the interactions between climate and grazing on functions are based on meta-analyses [12][13][14] (i.e., unstandardized sampling and analytical approaches) and unstandardized field investigation (i.e., grazed and ungrazed grassland distributed in different sites) 15 . Yet, regional paired comparison and replicated site experiments investigating the impacts of grazing on biodiversity and multiple ecosystem functions are urgently needed to empirically determine the causal effects of grazing on biodiversity and multifunctionality. ...
Grazing by domestic herbivores is the most widespread land use on the planet, and also a major global change driver in grasslands. Yet, experimental evidence on the long-term impacts of livestock grazing on biodiversity and function is largely lacking. Here, we report results from a network of 10 experimental sites from paired grazed and ungrazed grasslands across an aridity gradient, including some of the largest remaining native grasslands on the planet. We show that aridity partly explains the responses of biodiversity and multifunctionality to long-term livestock grazing. Grazing greatly reduced biodiversity and multifunctionality in steppes with higher aridity, while had no effects in steppes with relatively lower aridity. Moreover, we found that long-term grazing further changed the capacity of above- and below-ground biodiversity to explain multifunctionality. Thus, while plant diversity was positively correlated with multifunctionality across grasslands with excluded livestock, soil biodiversity was positively correlated with multifunctionality across grazed grasslands. Together, our cross-site experiment reveals that the impacts of long-term grazing on biodiversity and function depend on aridity levels, with the more arid sites experiencing more negative impacts on biodiversity and ecosystem multifunctionality. We also highlight the fundamental importance of conserving soil biodiversity for protecting multifunctionality in widespread grazed grasslands.
... Results from our field study illustrate that precipitation reduction elicited a cascade of events that shifted plant composition, and enhanced plant growth, root turnover, and microbia l N mineralization, thereby promoting N2O emissions via nitrification. Our incubation experime nt showed that drying-rewetting cycles amplified the legacy effect of field precipitation reduction on Also, farmers employ high N inputs and irrigation in many croplands on the Loess plateau (Huang & Shao, 2019) and other semi-arid regions (Maestre et al., 2022). These systems may become hotpots of N2O emissions and a comprehensive understanding of related microbial processes would help design management regimes of N and water to minimize N2O emissions. ...
The ongoing climate change is predicted to induce more weather extremes such as frequent drought and high-intensity precipitation events, causing more severe drying-rewetting cycles in soil. However, it remains largely unknown how these changes will affect soil nitrogen (N)-cycling microbes and the emissions of potent greenhouse gas nitrous oxide (N2 O). Utilizing a field precipitation manipulation in a semi-arid grassland on the Loess Plateau, we examined how precipitation reduction (ca. -30%) influenced soil N2 O and carbon dioxide (CO2 ) emissions in field, and in a complementary lab-incubation with simulated drying-rewetting cycles. Results obtained showed that precipitation reduction stimulated plant root turnover and N-cycling processes, enhancing soil N2 O and CO2 emissions in field, particularly after each rainfall event. Also, high-resolution isotopic analyses revealed that field soil N2 O emissions primarily originated from nitrification process. The incubation experiment further showed that in field soils under precipitation reduction, drying-rewetting stimulated N mineralization and ammonia-oxidizing bacteria in favor of genera Nitrosospira and Nitrosovibrio, increasing nitrification and N2 O emissions. These findings suggest that moderate precipitation reduction, accompanied with changes in drying-rewetting cycles under future precipitation scenarios, may enhance N cycling processes and soil N2 O emissions in semi-arid ecosystems, feeding positively back to the ongoing climate change.
The replacement of grasses by shrubs or bare ground (xerification) is a primary form of landscape change in drylands globally with consequences for ecosystem services. The potential for wild herbivores to trigger or reinforce shrubland states may be underappreciated, however, and comparative analyses across herbivore taxa are sparse. We sought to clarify the relative effects of domestic cattle, native rodents, native lagomorphs, and exotic African oryx (Oryx gazella) on a Chihuahuan Desert grassland undergoing shrub encroachment. We then asked whether drought periods, wet season precipitation, or interspecific grass–shrub competition modified herbivore effects to alter plant cover, species diversity, or community composition. We established a long‐term experiment with hierarchical herbivore exclosure treatments and surveyed plant foliar cover over 25 years. Cover of honey mesquite (Prosopis glandulosa) proliferated, responding primarily to climate, and was unaffected by herbivore treatments. Surprisingly, cattle and African oryx exclusion had only marginal effects on perennial grass cover at their current densities. Native lagomorphs interacted with climate to limit perennial grass cover during wet periods. Native rodents strongly decreased plant diversity, decreased evenness, and altered community composition. Overall, we found no evidence of mammalian herbivores facilitating or inhibiting shrub encroachment, but native small mammals interacting with climate drove dynamics of herbaceous plant communities. Ongoing monitoring will determine whether increased perennial grass cover from exclusion of native lagomorphs and rodents slows the transition to a dense shrubland.
Understanding what regulates ecosystem functional responses to disturbance is essential in this era of global change. However, many pioneering and still influential disturbance‐related theorie proposed by ecosystem ecologists were developed prior to rapid global change, and before tools and metrics were available to test them. In light of new knowledge and conceptual advances across biological disciplines, we present four disturbance ecology concepts that are particularly relevant to ecosystem ecologists new to the field: (a) the directionality of ecosystem functional response to disturbance; (b) functional thresholds; (c) disturbance–succession interactions; and (d) diversity‐functional stability relationships. We discuss how knowledge, theory, and terminology developed by several biological disciplines, when integrated, can enhance how ecosystem ecologists analyze and interpret functional responses to disturbance. For example, when interpreting thresholds and disturbance–succession interactions, ecosystem ecologists should consider concurrent biotic regime change, non‐linearity, and multiple response pathways, typically the theoretical and analytical domain of population and community ecologists. Similarly, the interpretation of ecosystem functional responses to disturbance requires analytical approaches that recognize disturbance can promote, inhibit, or fundamentally change ecosystem functions. We suggest that truly integrative approaches and knowledge are essential to advancing ecosystem functional responses to disturbance.
How the multiple facets of soil fungal diversity vary worldwide remains virtually unknown, hindering the management of this essential species-rich group. By sequencing high-resolution DNA markers in over 4000 topsoil samples from natural and human-altered ecosystems across all continents, we illustrate the distributions and drivers of different levels of taxonomic and phylogenetic diversity of fungi and their ecological groups. We show the impact of precipitation and temperature interactions on local fungal species richness (alpha diversity) across different climates. Our findings reveal how temperature drives fungal compositional turnover (beta diversity) and phylogenetic diversity, linking them with regional species richness (gamma diversity). We integrate fungi into the principles of global biodiversity distribution and present detailed maps for biodiversity conservation and modeling of global ecological processes.
Introduction
Livestock overgrazing represents one of the most destructive uses of land in terrestrial ecosystems and threatens biodiversity. However, understanding the effects of livestock overgrazing on below‐ground soil microbial diversity is limited, despite soil microbes representing the majority of biodiversity and determining ecosystem functioning.
Materials and Methods
To investigate the effects of overgrazing on soil microbial richness, a long‐term grazing exclusion experiment was conducted at six sites including three meadow steppes and three typical steppes in northern China.
Results
Our results revealed that overgrazing decreased bacterial and fungal richness across temperate steppes in northern China, and the biome could regulate the overgrazing effects, especially for fungal richness. Specifically, the negative effects of overgrazing on microbial richness were highly significant in typical steppes while not significant in meadow steppes that contained higher plant diversity and precipitation. Partial least‐squares path model showed that overgrazing affected soil microbial richness in highly complex ways, and the affected pathways were different in meadow steppes and typical steppes. The direct negative effects of grazing and their indirect negative effects via soil properties resulted in a significant decrease in microbial richness in typical steppes. In meadow steppes, the indirect beneficial effects via plant attributes offset the direct negative effects of grazing. Consequently, the soil microbial community in meadow steppe resisted overgrazing disturbance.
Conclusion
Our study illuminates the complex and highly biome‐dependent grazing effects and pathways on soil microbiota and indicates that meadow steppe may be more resistant or resilient to human disturbance than typical steppe. These findings suggest that different grasslands might be managed differently considering their intrinsic characteristics to help biodiversity conservation. Moreover, future research should focus on the underlying mechanisms of grazing effects on soil microbial richness. Besides grazing‐induced plant and soil traits changes, other potential pathways could strongly influence soil microbial diversity.
The temporal stability of grassland plant communities is substantially affected by soil nutrient enrichment. However, the potential main and interactive effects of arbuscular mycorrhizal fungi (AMF) and soil nitrogen (N) and phosphorus (P) enrichment on the stability of plant productivity have not yet been clarified. We combined a three‐year in situ field experiment to assess the impacts of soil fertilization and AMF on the stability of plant productivity. P addition decreased the stability of plant productivity by increasing the standard deviation relative to the mean of plant productivity. However, compared to species richness, the stability of C 3 grasses and other functional groups asynchrony were the most important drivers changing the stability of plant productivity. The negative impacts of P addition overrode the impacts of AMF on the stability of plant productivity. Overall, our study suggests the importance of soil nutrient availability over AMF in terms of shaping the stability of plant productivity. Our results also suggest that three‐year anthropogenic soil nutrient enrichment could reduce the stability of plant communities in grassland regardless of AMF in the P‐limited grassland ecosystem.
Human activities, directly and indirectly, impact ecological engineering activities of subterranean rodents. As engineering activities of burrowing rodents are affected by, and reciprocally affect vegetation cover via feeding, burrowing and mound building, human influence such as settlements and livestock grazing, could have cascading effects on biodiversity and ecosystem processes such as bioturbation. However, there is limited understanding of the relationship between human activities and burrowing rodents. The aim of this study was therefore to understand how human activities influence the ecological engineering activity of the giant root-rat (Tachyoryctes macro-cephalus), a subterranean rodent species endemic to the Afroalpine ecosystem of the Bale Mountains of Ethiopia. We collected data on human impact, burrowing activity and vegetation during February and March of 2021. Using path analysis, we tested (1) direct effects of human settlement on the patterns of livestock grazing intensity, (2) direct and indirect impacts of humans and livestock grazing intensity on the root-rat burrow density and (3) whether human settlement and livestock grazing influence the effects of giant root-rat burrow density on vegetation and vice versa. We found lower levels of livestock grazing intensity further from human settlement than in its proximity. We also found a significantly increased giant root-rat burrow density with increasing livestock grazing intensity. Seasonal settlement and livestock grazing intensity had an indirect negative and positive effect on giant root-rat burrow density, respectively, both via vegetation cover. Analysing the reciprocal effects of giant root-rat on vegetation, we found a significantly decreased vegetation cover with increasing density of giant root-rat burrows, and indirectly with increasing livestock grazing intensity via giant root-rat burrow density. Our results demonstrate that giant root-rats play a synanthropic engineering role that affects vegetation structure and ecosystem processes. K E Y W O R D S bioturbation, grazing intensity, human settlement, rodent burrow, synanthropic association
Our planet teeters on the brink of massive ecosystem collapses, and arid regions experience manifold environmental and climatic challenges that increase the magnitude of selective pressures on already stressed ecosystems. Ultimately, this leads to their aridification and desertification, that is, to simplified and barren ecosystems (with proportionally less microbial load and diversity) with altered functions and food webs and modification of microbial community network. Thus, preserving and restoring soil health in such a fragile biome could help buffer climate change's effects. We argue that microorganisms and the protection of their functional properties and networks are key to fight desertification. Specifically, we claim that it is rational, possible and certainly practical to rely on native dryland edaphic microorganisms and microbial communities as well as dryland plants and their associated microbiota to conserve and restore soil health and mitigate soil depletion in newly aridified lands. Furthermore, this will meet the objective of protecting/stabilizing (and even enhancing) soil biodiversity globally. Without urgent conservation and restoration actions that take into account microbial diversity, we will ultimately, and simply, not have anything to protect anymore.
Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and species-poor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure.
Plant-soil microbe linkage is theoretically positive, but rarely observed in natural ecosystems. We hypothesized that animal grazing decouples this linkage, for plant removal usually decreases plant influences on soil microbiota. We tested the hypothesis by exploring plant and soil microbial diversity in grazed versus non-grazed grasslands along a gradient of plant diversity. Grazing slightly decreased the diversity of plants and soil microbes in high-diversity sites, but increased them in low-diversity sites. Plant and microbial diversity positively correlated in non-grazed grasslands (P < 0.001), but not in grazed grasslands, indicating that grazing decoupled the biodiversity linkage. The decoupling was attributed to the change of the principal driver of soil microbiota from plant variables in non-grazed grasslands to soil variables in grazed grasslands. The diversity decoupling was also characterized by reduced plant-microbe interactions and lower heterogeneity in grazed grasslands. Our findings provide significant insights into the cross-biota linkages in grassland ecosystems.
Livestock grazing is a major driver shaping grassland biodiversity, functioning and stability. Whether grazing impacts on grassland ecosystems are scale- dependent remains unclear. Here, we conducted a sheep- grazing experiment in a temperate grassland to test grazing effects on the temporal stability of productivity across scales. We found that grazing increased species stability but substantially de-creased local community stability due to reduced asynchronous dynamics among species within communities. The negative effect of grazing on local community stability propagated to reduce stability at larger spatial scales. By decreasing biodi-versity both within and across communities, grazing reduced biological insurance effects and hence the upscaling of stability from species to communities and fur-ther to larger spatial scales. Our study provides the first evidence for the scale de-pendence of grazing effects on grassland stability through biodiversity. We suggest that ecosystem management should strive to maintain biodiversity across scales to achieve sustainability of grassland ecosystem functions and services.
Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and species-poor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure.
- Z Mehrabi
- M Gill
- M Van Wijk
- M Herrero
- N Ramankutty
Z. Mehrabi, M. Gill, M. van Wijk, M. Herrero, N. Ramankutty,
Nat. Food 1, 160-165 (2020).
- D G Milchunas
- W K Lauenroth
D. G. Milchunas, W. K. Lauenroth, Ecol. Monogr. 63, 327-366
(1993).
- D J Eldridge
- A G B Poore
- M Ruiz-Colmenero
- M Letnic
- S Soliveres
D. J. Eldridge, A. G. B. Poore, M. Ruiz-Colmenero, M. Letnic,
S. Soliveres, Ecol. Appl. 26, 1273-1283 (2016).
- K Petz
K. Petz et al., Glob. Environ. Change 29, 223-234 (2014).
- D J Eldridge
- M Delgado-Baquerizo
- Land Degrad
D. J. Eldridge, M. Delgado-Baquerizo, Land Degrad. Dev. 28,
1473-1481 (2017).
- J J Gaitán
J. J. Gaitán et al., Land Degrad. Dev. 29, 210-218 (2018).
- A Linstädter
A. Linstädter et al., PLOS ONE 9, e104672 (2014).
- P Manzano
P. Manzano et al., One Earth 4, 651-665 (2021).
- S E Koerner
S. E. Koerner et al., Nat. Ecol. Evol. 2, 1925-1932 (2018).
Sustainable Land Management, Food Security, and Greenhouse Gas Fluxes in Terrestrial Ecosystems
- A Mirzabaev
A. Mirzabaev et al., in Climate Change and Land: An IPCC
Special Report on Climate Change, Desertification, Land
Degradation, Sustainable Land Management, Food Security,
and Greenhouse Gas Fluxes in Terrestrial Ecosystems, et al.,
Eds. (Intergovernmental Panel on Climate Change, 2019),
pp. 249-344.
- F T Maestre
F. T. Maestre et al., Science 335, 214-218 (2012).
- M Delgado-Baquerizo
M. Delgado-Baquerizo et al., Nat. Commun. 7, 10541 (2016).
- N M Gadzama
N. M. Gadzama, World J. Sci. Technol. Sustain. Dev. 14,
279-289 (2017).
- J Chang
J. Chang et al., Nat. Commun. 12, 118 (2021).
- P García-Palacios
P. García-Palacios et al., Nat. Rev. Earth Environ. 2, 507-517
(2021).
- J E Duffy
- C M Godwin
- B J Cardinale
J. E. Duffy, C. M. Godwin, B. J. Cardinale, Nature 549, 261-264
(2017).
- E S Forbes
E. S. Forbes et al., Funct. Ecol. 33, 1597-1610 (2019).
- L Wang
L. Wang et al., Proc. Natl. Acad. Sci. U.S.A. 116, 6187-6192 (2019).
- J P G M Cromsigt
J. P. G. M. Cromsigt et al., Philos. Trans. R. Soc. London Ser. B
373, 20170440 (2018).
- C Almer
- J Laurent-Lucchetti
- M Oechslin
C. Almer, J. Laurent-Lucchetti, M. Oechslin, J. Environ. Econ.
Manage. 86, 193-209 (2017).
- S A Mousavi
- M Ghahfarokhi
- S Soltani
- Koupaei
S. A. Mousavi, M. Sarshad Ghahfarokhi, S. Soltani Koupaei,
Ecol. Indic. 110, 105946 (2020).
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SUPPLEMENTARY MATERIALS
science.org/doi/10.1126/science.abq4062
Materials and Methods
Figs. S1 to S19
Tables S1 to S28
References (33-269)