Increasing Livestock Densities Research Articles

Gridded livestock density database and spatial trends for Kazakhstan

Livestock rearing is a major source of livelihood for food and income in dryland Asia. Increasing livestock density (LSKD) affects ecosystem structure and function, amplifies the effects of climate change, and facilitates disease transmission. Significant knowledge and data gaps regarding their density, spatial distribution, and changes over time exist but have not been explored beyond the county level. This is especially true regarding the unavailability of high-resolution gridded livestock data. Hence, we developed a gridded LSKD database of horses and small ruminants (i.e., sheep & goats) at high-resolution (1 km) for Kazakhstan (KZ) from 2000–2019 using vegetation proxies, climatic, socioeconomic, topographic, and proximity forcing variables through a random forest (RF) regression modeling. We found high-density livestock hotspots in the south-central and southeastern regions, whereas medium-density clusters in the northern and northwestern regions of KZ. Interestingly, population density, proximity to settlements, nighttime lights, and temperature contributed to the efficient downscaling of district-level censuses to gridded estimates. This database will benefit stakeholders, the research community, land managers, and policymakers at regional and national levels.

Carbon and nutrient budgets of the Chagga home garden system in the Kilimanjaro highlands, Tanzania

AbstractSustainable land management of smallholder farms is crucial for ensuring food security in sub‐Saharan Africa. However, little is known about the nutrient dynamics of smallholder farming systems at the farm level based on primary data. In this study, carbon (C) and nutrient budgets of the home garden system in the Kilimanjaro highlands, where Andosols predominate, were quantified at the farmer's field. We evaluated (1) the soil C and nutrient flow in the main three land‐use blocks (banana (Musa spp.) garden, maize (Zea mays L.) field and grassland) in one representative home garden and (2) the internal flow between farmland and livestock and the external nutrient flow across the inside and outside of the six home gardens. Intensive applications of livestock dung to the banana trees resulted in a positive C budget (7.2 Mg C ha−1 year−1) in the banana garden. Nitrogen loss through the harvesting of feed and crops was almost balanced with the livestock dung application, while nitrogen loss through leaching only accounted for 3% of that applied. Banana productivity has been maintained despite a negative potassium budget (−241 kg K ha−1 year−1), probably owing to the replenished exchangeable potassium from Andosols. In the maize field, the C budget was negative (−1.7 Mg C ha−1 year−1) owing to high organic matter decomposition. Carbon and nutrient budgets in the grassland were all negative. Our results revealed that the village average livestock density (4.4 TLU ha−1: TLU means tropical livestock unit) was sufficient for P, Ca and Mg balance in the home garden, whereas it was not sufficient for N and K balance. Increasing livestock density improved the nutrient balance of the system. However, it is noteworthy that 33%–47% of the feed supplied as C and nutrients was collected from outside the home gardens, suggesting a high reliance on external inflow to fulfil feed demands. In conclusion, intensive livestock dung application to banana cultivation was fundamental for maintaining agricultural productivity to replenish the nutrients lost from the system. At the same time, this system was sustained not only by C and nutrient cycling within the system, but also by transporting resources from the external environment into the system.

Combined Effects of Clime, Vegetation, Human-Related Land Use and Livestock on the Distribution of the Three Indigenous Species of Gazelle in Eritrea.

The status and habitat selection of the three species of gazelle indigenous to Eritrea, i.e., Nanger soemmerringii, Gazella dorcas and Eudorcas tilonura, are not well known. In this study, we analyzed the present distribution of the three species in the country in order to identify preferred habitats and assess the effect of human disturbance (land use for agricultural purposes and livestock) on species occurrence. These data represent baseline information for evidence-based strategies for conservation of the three species in Eritrea. Presence/absence data of the three species in each of the 67 administrative subregions (Sub Zoba) composing the country were collected using direct (field surveys) and indirect methods (questionnaires). For each sampling unit, we collected fifteen environmental variables, of which three are associated with climatic features, eight with vegetation structure and four with human disturbance (human-related land use and livestock). The occurrence probability of each species was modeled through Generalized Linear Models (GLM). The analyses showed that Dorcas gazelle occurred more frequently in warmer conditions and in a wide range of natural vegetation types. Heuglin's gazelle occurred in warmer regions with higher seasonality in both temperature and precipitation with a preference for closed woody and open grassland areas. In the case of Soemmerring's gazelle, the GLM with climatic variables predicted a preference for warmer conditions but with lower seasonality of temperature and precipitation. The species also seemed to prefer arid and semi-arid open vegetation. Human disturbance is the variable with the strongest, negative, effect on the species occurrence. Indeed, the occurrence probability of each species decreased with increasing livestock density and agricultural land use. Most of these gazelle occurred in unprotected areas, thus the human-related activities are undoubtedly the most important threat for the three species of gazelle in Eritrea. Therefore, the establishment of protected areas that preserve the potential optimal habitats for gazelle and reduce the impact of livestock ranching are essential to ensure a future for these gazelle in Eritrea.

Coupled biophysical and decision-making processes in grassland systems in East African savannahs – A modelling framework

Increasing livestock densities on limited grazing areas in African savannahs lead to resource degradation through overgrazing, aggravated by drought. Assessing herd management strategies over longer periods at landscape scale is important to propose options for sustainable land use. This requires an understanding of processes related to hydrology, nutrient cycling, herd movement, pasture degradation, and animal resilience that involve dynamic soil-plant-animal interactions and human decisions about stocking rates, livestock purchases and sales.We present the coupled model system MPMAS-LUCIA-LIVSIM (MLL), the combination of a spatially explicit agent-based model for human decision-making (MPMAS), a spatially distributed landscape model for water flows, nutrient cycles and plant growth (LUCIA), and a herd model (LIVSIM) representing grazing, body weight, nutrition and excreta of individual animals. MLL represents daily vegetation growth in response to grazing and organic inputs, monthly animal performance influenced by forage availability and quality, and herders’ management in response to resource status. New modules for selective grazing, resprouting of pasture, herd movement and model coupling were developed for MLL.The test case of a pastoral system in the Ethiopian Borana region demonstrates the capabilities of MLL to simulate key soil-plant-animal-human interactions under climate-related management scenarios with varying access to grazing land, changing cattle prices and different spending / saving behaviour of herders. 20-year simulations showed the negative impact of consecutive drought years on vegetation biomass, on herd development and movement and how reserving grazing areas for dry seasons could mitigate overgrazing and improve income. Seasonality and drought response of vegetation growth, selective grazing of different plant parts, resprouting after grazing, calving intervals, milk yields and lactation in response to forage supply and quality as well as herder reactions to shocks were plausibly represented.Building upon this successful proof-of-concept, MLL can be used to identify robust management options for improved grazing systems in savannahs in follow-up research.

Economic valuation of grassland utilization improvement in the Western Balkans

Grassland is land permanently overgrown with grasses that can be used for grazing or preparing fodder. When identifying and delineating grassland areas from other agricultural areas, criteria can be their purpose (land cover) or their use (land use). The processes of depopulation and deagrarization of rural areas increase the surfaces of unutilized grasslands and decrease of their use for agricultural purpose. The purpose of research presented in this paper is the analysis of transformation of grassland area in six Western Balkans countries/territories from covered to used status. During the research, the methods of quantitative modelling and simulation were combined. Starting from existing grassland areas (which are equalized with permanent meadows and pastures), the intensity of their use was determined by calculating the grazing livestock density (GLD) index. Generally, grasslands are used extensively for feeding ruminants in the WB region, and great part of the area is not used at all, so the average GLD index is 0.88 with significant variations between countries. Three countries (Bosnia and Herzegovina, Montenegro and North Macedonia) have a GLD of 0.5 or less and there is space for them to increasing the number of ruminants up to 1.1 million livestock standard units (LSU) and increasing livestock density up to one LSU per ha of grassland. The conclusion is that, depending on the scenario, i.e. the structure of ruminant stock (cattle, sheep and goats), the value of livestock production in the Western Balkans could increase from 498 to 655 million EUR, still without environmental pressure of grazing on grassland area.

Livestock indirectly decrease nest abundance of two shrub-nesting species in Patagonian Monte Desert

Domestic livestock may indirectly affect bird species through changes in vegetation structure (e.g. cover), reducing the availability of food, nesting sites, refugia and, therefore, reproduction in many ecosystems worldwide. However, it remains unclear how the effect of livestock on vegetation structure can influence insectivorous birds that use shrubs for nest construction and placement rather than for feeding. Several species from the Furnariidae family inhabit Monte Desert, Argentina, exhibiting an extraordinary diversity in nest placement and structure that allows them to survive habitat aridity. Nest abundance and size of two common furnariid species, Pseudoseisura gutturalis and Leptasthenura aegithaloides, were studied across a cumulative livestock impact gradient (livestock impact by years grazed). These bird species use large, closed-nests (~40cm and ~100cm length, respectively) built with thorny branches placed on thorny shrubs. The study encompassed nine independent rangelands within the same habitat, but with increasing livestock density, establishing a gradient in grazing intensity. In each rangeland, nest abundance, nest and supporting plant characteristics, vegetation structure and the percentage of browsing were assessed. Plant cover was lower in rangelands with higher livestock impact, and this was associated with lower nest abundance and nest size. Nest abundance of L. aegithaloides was halved, whereas P. gutturalis was decreased 10-fold comparing the extremes of the livestock impact gradient (0.06 vs 1.63 cattle ha−1×years). Nests tended to be smaller and more spherical with increasing livestock impact. The significant and positive association between nest abundance and vegetation structure together with the importance of mating and reproduction for bird lifecycles suggests that the nest abundance of these species could be used as an indicator of habitat degradation. Therefore, furnariid nest abundance could be used as a first step for diagnosing ecosystem health and designing ecologically sustainable management practices in Monte Desert. Changes in vegetation structure (e.g. cover) such as those imposed by livestock may unpredictably affect plant-associated species affecting their reproduction, demography and ecosystem biodiversity.

How compatible are urban livestock and urban green spaces and trees? An assessment in a medium-sized South African town

ABSTRACTUrban green spaces and trees provide multiple benefits to urban residents and the sustainability of cities. A poorly examined benefit is the provision of fodder to urban livestock. However, the presence and activities of livestock may be incompatible with other uses, although this has been little studied. We examined the impacts of livestock on trees and parks along a gradient of declining livestock density, complemented with a tree planting experiment to monitor damage. Neighbouring residents and park managers were interviewed regarding their perceptions of damage caused by livestock. The negative impacts on soil compaction, tree damage and death increased with increasing livestock densities. Thorny tree species were damaged significantly less (13 %) than non-thorny species (77 %), as were protected trees (25 %) relative to unprotected ones (65 %). There was more tree damage in public green spaces (PUGS) (54 %) than control sites (38 %). The majority of local residents felt that livestock should not be allowed in formal PUGS, and most urban park managers regarded livestock damage as a strong disincentive to plant trees. These results show the need for management of the trade-offs caused by livestock and greater appreciation of livestock as agents shaping aspects of PUGS.

Sequential stable isotope analysis reveals differences in multi-year dietary history of three sympatric equid species in SW Mongolia.

Summary Competition among sympatric wild herbivores is reduced by different physiological, morphological and behavioural traits resulting in different dietary niches. Wild equids are a rather uniform group of large herbivores which have dramatically declined in numbers and range. Correlative evidence suggests that pasture competition with livestock is one of the key factors for this decline, and the situation may be aggravated in areas where different equid species overlap.The Dzungarian Gobi is currently the only place where two wild equid species coexist and share the range with the domesticated form of a third equid species. In the winter‐cold Gobi desert pasture productivity is low, highly seasonal, and wild equids additionally face increasing livestock densities.We used stable isotope chronologies of tail hairs to draw inferences about multi‐year diet seasonality, isotopic dietary niches and physiological adaptations in the Asiatic wild ass (khulan), re‐introduced Przewalski's horse, and domestic horse in the Mongolian part of the Dzungarian Gobi.Our results showed that even in the arid Gobi, both horse species are predominantly grazers, whereas khulan are highly seasonal, switching from being grazers in summer to mixed feeders in winter. The isotopic dietary niches of the two horse species were almost identical, did not vary with season as in khulan and were narrower than in the latter. Higher δ15N values point towards higher water use efficiency in khulan, which may be one reason why they can exploit pastures further away from water. Synthesis and applications. The high degree of isotopic dietary niche overlap in the two horse species in the Mongolian Gobi points towards a high potential for pasture competition during the critical nutritional bottleneck in winter and highlights the need to severely restrict grazing of domestic horses on the range of the Przewalski's horses. The evolutionary more distant khulan are less constrained by water and seem more flexible in their choice of diet or less successful in exploiting grass‐dominated habitats in winter due to human presence. Providing additional water sources could increase the competition between khulan and livestock and should, therefore, only be done following careful consideration.

Unexpectedly, intense livestock grazing in arid rangelands strengthens the seedling vigor of consumed plants

Grazing intensification with non-native livestock is known to degrade vegetation cover, particularly in arid environments where low resource availability strongly limits plant recovery after damage. However, it remains unclear whether the effect of grazing on consumed plants is transmitted to plant offspring. We hypothesized that grazing would reduce fruit weight, germination percentage, and seedling vigor of consumed vegetation. Therefore, we collected mature fruits from six dominant shrub species in seven independent paddocks with increasing livestock densities. Fruits were air-dried and weighed before seed sowing. After seedling emergence, we measured the percentage of germination and seedling vigor, i.e., height and number of leaves. Hierarchical models were used to account for the effects of plant species and year of collection. Results show that, in general, increasing livestock density reduced fruit weight and percentage of germination of consumed plants. However, surprisingly, increasing livestock density enhanced seedling vigor. Overall, increasing livestock density has both negative and positive effects on consumed plantsʼ offspring.

Landscape variables that influence the presence of brocket deer (Mazama sp.) in the Campeche State, México

The brocket deer (Mazama temama and M. pandora) are two of the Mexican tropical deer with great importance for subsistence and sport hunters. Brocket deer are considered species with preference for pristine habitats conserved, however at the landscape level, factors such as hunting pressure could influence the presence and abundance of these species. Campeche, is the only Mexican state where it has been authorized the exploitation of the brocket deer for sport hunting. This hunting pressure along with the intense subsistence hunting that occurs in Campeche, could have important effects on the conservation of the species. Establishing what factors determine the presence of the species at the landscape level is essential to elaborate comprehensive management plans of these species to allow their long-term conservation. The aim of this study was to determine the habitat variables at the landscape level that influence the brocket deer presence in the central-western area of Campeche State in Mexico. The study area in the state of Campeche (19° 15’ N, -91o 20´ W) was divided into six study regions (Chekubul-Cristalina; Chenkan; Chicbul-Km 74; Pixtun-Felipe Carrillo Puerto, Miguel Colorado; Centenario-La Riguena) following the main paved road of the area and according to the conservation level of the natural ecosystems, presence of flooded areas, and intensity of the human activities where we determine the presence of brocket deer. We searched for brocket deer tracks along 263 transects of 500 m each. The tracks were identified to genus only. The presence/absence of brocket deer in the transects was combined with variables of human and natural origin of the study area in a geographical information system. We use principal component analysis and a logistic regression to determine the relationship between variables and the presence/absence of the brocket deer. We were not able to distinguish by their tracks the two potentially distributed species of brocket deer in the area. Due to this constraint, we did not perform a distinction between both species and all the observed tracks were classified as brocket deer. We found that brocket deer were present only in three of the six studied regions: Miguel Colorado (21.3 % transect had brocket deer presence), Centenario-La Riguena (20.4 %) and Chenkan (1.7 %). The principal component analysis indicated that the variables determining the presence of brocket deer were, the percentage of preserved forest and distance to pastures, positively associated, while livestock density was negative. The best model obtained by the logistic regression showed that the presence of brocket deer increased when the percentage of preserved forests around transect is increased, while decreasing with increasing livestock density. The presence of conserved forests favors the presence of brocket deer in the study area, while a higher density of cattle decreases the probability of detection. The few records of brocket deer in flooded zones in this study and the lack of detection of the species in previous studies, suggests that these flooded ecosystems may not be suitable for brocket deer, which would have a strong impact on their known distributional range. Finding that brocket deer are present mainly in preserved sites indicates the species could be subject to an intense population reduction in the study area due to the continued habitat loss. The results suggest that before granting authorizations for sport hunting in this region, it is necessary to make accurate estimates of the population distribution and abundance of the species in the region.

Variation in Insect Assemblage and Functional Groups along a Grazing Gradient in an Arid Environment

Exotic livestock may affect plant and pollinator composition as well as their interactions. Changes in pollinator assemblage (e.g. composition) may alter pollination process and, therefore, plant reproduction. This study examined seven independent paddocks environmentally similar but with increasing livestock densities, in Patagonian Monte Desert. This allows investigating the response of different insect groups to livestock effect on vegetation along a grazing gradient. Water traps was used to capture insects (focusing on pollinators) and pollinator visitation frequencies were measured in five of the most abundant native plant species of the region. Regressions between livestock density and insect richness and abundance of the different functional groups of insects (dipterans, herbivores and pollinators) were performed. Insect assemblage was mostly composed, in decreasing order, by hymenopterans, coleopterans, dipterans and lepidopterans. Ordination analysis of insect composition showed a high correlation between the first axis and livestock density (r=0.95). In the first year of sampling, pollinators significantly decreased in richness and wasps increased in abundance with livestock density. In the second year of sampling, pollinator abundance increased and herbivores decreased as livestock density increased. Unimodal ordination analyses showed that plant species were significantly associated to insect composition and livestock density marginally explained the variation in insect composition that visited the five studied plant species across paddocks. Interacting factors such as livestock density and climatic conditions may partially explain the patterns observed in this work. Disturbances may alter the ecological scenarios, impoverishing the composition and abundance of flora and fauna. This study describes that changes in the density of exotic livestock can affect insect assemblage associated to pollination process differently through the years. Changes through time may determine population dynamic and their response to anthropogenic disturbances

Sympatric guanacos and livestock share water resources in drylands of Argentina

AbstractThere is growing concern about the effect of livestock on wild ungulate populations, particularly in arid ecosystems, where waterholes are an extremely scarce resource, around which animals tend to gather, primarily in the dry season. This situation is worrying in South American deserts, where guanaco is the native species that often shares trophic and water resources with livestock from local communities, even inside protected areas. We assess through general linear modeling (GLM) the use of waterholes by guanaco and two introduced species, free-ranging cattle and feral donkeys, during the summer-wet and winter-dry seasons, in an arid, water-limited region in northwestern Argentina. Waterholes were more intensively used in the dry than the wet season by all three herbivores. However, introduced ungulates did not use all of the waterholes, whereas guanaco used them all with equal intensity, which points to an apparent absence of interference probably due to the low density of the introduced species. Nevertheless these results could mask negative effects regarding the risk of parasite transmission, the under-use of one of the waterholes, and the risk related to increasing livestock density in a near future. Therefore, it would be advisable to make long-term monitoring to prevent potentially negative effects on guanacos.

Effects of crop and livestock segregation on phosphorus resource use: A systematic, regional analysis

The integration of crops and animals is an option to reduce mineral fertiliser use through the recycling of nutrients in animal manure on croplands. But the increasing specialisation and spatial segregation of crop and livestock production systems both at the farm and the district scale may hamper the proper recycling of nutrients between these two activities. However, the effect of such segregation has only been investigated on some case-studies – mostly at the regional and the local scale – while we still lack of systematic assessment of this segregation in terms of mineral fertiliser use on a range of scales. In this paper, we estimated the effect of this segregation on nutrient resource use at the district scale. Phosphorus (P) fertiliser was considered since it is produced from a finite resource that needs to be more efficiently recycled in agriculture and France was chosen as a case study, representative of industrial countries with a wide range of variations in crop and livestock segregation. We quantified the effect of livestock density on mineral P fertiliser use and the effect of crop and livestock spatial segregation on P fertiliser use and its substitution with P in animal manure. Our results showed that P fertiliser use decreased with increasing livestock density at the district scale. However, the substitution of P fertiliser with P in animal manure was only partial (probably due to more N- than P-oriented decision making by farmers and low N:P ratio of organic manure), leading to large nutrient surpluses in districts with high livestock densities (>1.1 livestock unit per agricultural area). Finally, P fertiliser use increased with the spatial segregation of crops and livestock. Overall, our results demonstrated that lower segregation of crops and animals could help to save non-renewable resources, and that improvements in manure management are required.

Mongolian rangelands at a tipping point? Biomass and cover are stable but composition shifts and richness declines after 20 years of grazing and increasing temperatures

Mongolian rangelands have experienced warming temperatures and increasing livestock densities over the past 20 years. Remote sensing studies report widespread degradation, but there are no long-term field studies of vegetation responses to shifts in climate and stocking densities.In 2013, we resampled plots originally sampled in 1994–1995 in the desert-steppe, steppe and mountain-steppe, and analyzed changes in vegetation in relation to changes in climate, stocking densities and forage use. Summer temperatures significantly increased and stocking densities fluctuated in response to droughts followed by harsh winters. Total herbaceous biomass in 2013 was similar to (desert-steppe and steppe) or greater than (mountain-steppe) in 1995, and total foliar and herbaceous cover were unchanged since 1995 in all zones. In the mountain-steppe, functional type and species cover shifts were consistent with warming temperatures and increasing grazing pressure. All species richness and diversity indicators declined significantly in the mountain-steppe since 1995, as did richness in the steppe. Some Mongolian rangelands may be losing resilience due to interacting climate and grazing pressures, but our data suggest degradation observed at our study sites is reversible. Mountain-steppe systems appear more vulnerable to grazing- and climate-induced vegetation change than steppe and desert-steppe.

Methane in Australian agriculture: current emissions, sources and sinks, and potential mitigation strategies

Methane is a potent greenhouse gas with a global warming potential ~28 times that of carbon dioxide. Consequently, sources and sinks that influence the concentration of methane in the atmosphere are of great interest. In Australia, agriculture is the primary source of anthropogenic methane emissions (60.4% of national emissions, or 3 260 kt–1 methane year–1, between 1990 and 2011), and cropping and grazing soils represent Australia’s largest potential terrestrial methane sink. As of 2011, the expansion of agricultural soils, which are ~70% less efficient at consuming methane than undisturbed soils, to 59% of Australia’s land mass (456 Mha) and increasing livestock densities in northern Australia suggest negative implications for national methane flux. Plant biomass burning does not appear to have long-term negative effects on methane flux unless soils are converted for agricultural purposes. Rice cultivation contributes marginally to national methane emissions and this fluctuates depending on water availability. Significant available research into biological, geochemical and agronomic factors has been pertinent for developing effective methane mitigation strategies. We discuss methane-flux feedback mechanisms in relation to climate change drivers such as temperature, atmospheric carbon dioxide and methane concentrations, precipitation and extreme weather events. Future research should focus on quantifying the role of Australian cropping and grazing soils as methane sinks in the national methane budget, linking biodiversity and activity of methane-cycling microbes to environmental factors, and quantifying how a combination of climate change drivers will affect total methane flux in these systems.

Effects of livestock on guanacoLama guanicoedensity, movements and habitat selection in a forest–grassland mosaic in Tierra del Fuego, Chile

AbstractLocally abundant ungulates often come into conflict with human activities. After a population collapse that reached its nadir in the 1970s, the guanacoLama guanicoepopulation in Tierra del Fuego, Chile, recovered and is now in conflict with sheep ranching and commercial logging. We studied the effects of livestock density and environmental factors on guanaco abundance and spatial ecology, using seasonal counts and radio-telemetry in a private protected area (Karukinka) and neighbouring ranches in a forest–grassland mosaic in Tierra del Fuego. Guanaco density was highest in low-elevation areas with more grassland cover and little snow accumulation in winter. In low-elevation areas, guanaco density decreased with increasing livestock density. Radio-tracked guanacos exhibited a partial migration pattern: two individuals migrated seasonally, selecting grasslands and avoiding forests mainly in summer, whereas six sedentary individuals used habitats according to their availability. Migratory guanacos spent the summer in Karukinka and winter on nearby ranches. High sheep densities and poor range condition on the ranches reduce key forage resources available to guanacos and may promote use of forests by guanacos, affecting forest regeneration and increasing conflict with logging. Current guanaco harvest by loggers may fail to reduce the impact of guanacos on logged-forest regeneration if guanaco spatial ecology and sheep management are not considered. Our results provide insight into the interactions among guanacos, forests and livestock ranching, and may be used to reduce conflicts and guide conservation in the Fuegian ecosystem.

An Empirical Water Budget Model As a Tool to Identify the Impact of Land-use Change in Stream Flow in Southeastern Australia

In western Victoria, Australia the water table and lake level in the Glenelg-Hopkins catchment have been declining for the last 15 years, and this is attributed to either the low rainfall over this time and/or a substantial change in land use. Stream flow modelling was carried out using monthly empirical water balance model (modified tanh function together with double mass curve analysis), on 37 stream gauges to assess whether the impact of land use change could be detected by a change in the magnitude of the resulting runoff. The empirical hydrological model was able to distinguish impact of land use change on stream flow from the climatic variables. There were substantial decreases in stream flow in the 1970s–1980s, probably related to increasing livestock densities in the region. Furthermore, the methodology can be a powerful tool to monitor and evaluate the possible impacts of future land use changes. It can be concluded that the use of such empirical hydrological modelling greatly improves the ability to analyse the impact of land use on catchment runoff. The model is a practical tool that can be readily used for identifying and quantifying the effect of landuse changes on catchment for water resource decision-making, which could be hardly possible using the time consuming, data hungry and expensive physical process models available.

Plant responses to agricultural intensification

Summary 1. A large proportion of the world's land surface is extensively managed for livestock production. In areas where livestock systems are becoming more intensive, a major challenge is to predict those plant species likely to decline, persist or increase as a result of agricultural intensification. 2. Most analyses develop inferences for frequent or abundant species, or rely on intensive studies of single species. A promising approach is to identify plant traits related to disturbance to enable inference to be made about changes in plant community composition. We used a Bayesian hierarchical model to analyse the response to agricultural intensification of 494 plant species of pastures and woodlands in southern Australia, and to identify how simple species' traits (life form, growth form and species origin) influence those responses. 3. The probability of occurrence of most species declined along the two intensification gradients, grazing intensity and soil phosphorous concentration, although the occurrence of a greater proportion of species was negatively correlated with soil phosphorous. Responses could be broadly predicted from both plant origin and plant traits, in particular growth form. 4. Native perennial geophytes, ferns and shrubs were most negatively affected by both gradients, while exotic annual grasses and forbs were more tolerant. Along the phosphorous gradient, 24 of the 30 most negatively affected plant species were native geophytes. Mean within-group responses masked considerable within- and between-species variation, particularly for the exotic species group which included species that responded both negatively and positively to intensification. 5. Synthesis and applications. The hierarchical model described here provides a powerful method for estimating individual plant responses and identifying how species' traits influence those responses. Plant species native to southern Australia are sensitive to grazing and phosphorous apparently due to a shared evolutionary history of low grazing intensity and low phosphorous soils. Invading exotic plants have faced strongly contrasting ecological filters, leading to a greater diversity of responses. Where grazing systems have been most intense, a small suite of exotics dominate. Maintaining native and functional plant diversity will necessitate limits being placed on intensive livestock management systems.

Nonparasitic Nematoda provide evidence for a linear response of functionally important soil biota to increasing livestock density

Soil acidity, nutrient availability and livestock density have a major influence on the belowground ecological community. As fast decomposition rates are due mostly to bacterial-based pathways and slower decomposition rates mostly to fungal-based pathways, it is helpful to condense empirical information in the so-called Nematode Channel Ratio (NCR). The NCR is shown to be a good indicator of efficiency in soil decomposition processes. We argue that in intensive agroecosystems, other fungivore members of the decomposer food web may outcompete the hyphal-feeding nematodes. We demonstrate how the NCR can be used to set ecological standards for sustainable use of the soil in agroecosystems. To summarize the interactions between the microbial resources and the decomposer nematofauna according to increasing land management, we propose the use of the fifth percentile as proxy for a sustainable environmental quality of grasslands on sandy soils, and the NCR mean as the upper threshold for low-stocked farms.

Recovery of wild large herbivores following livestock decline in a tropical Indian wildlife reserve

Summary Resource competition is an important process governing the impact of livestock on native wild mammalian herbivores, an issue acknowledged to be of global conservation concern. Resource competition occurs between species when their resources (habitat and diet) overlap and are limiting. Yet the evidence that livestock compete with wild herbivores has remained weak because resource limitation is often difficult to demonstrate in the field. This 2‐year field study at Bandipur National Park, India, examined livestock‐mediated resource limitation among five wild herbivore species: wild pig Sus scrofa, chital Axis axis, sambar Cervus unicolor, gaur Bos gaurus and Asian elephant Elephas maximus, by comparing their distribution and densities in adjoining livestock‐grazed and livestock‐free areas before, and after, a 49% decline in livestock density. During 2001, mean densities of wild grazers, gaur (0·11 ha−1), chital (1·51 ha−1) and elephant (0·61 ha−1), were, respectively, 132, 11 and six times higher in the livestock‐free area than in the adjacent livestock‐grazed area. Densities of gaur, chital and elephant showed a sharp declining relationship with increasing livestock density, whereas no clear pattern was discernible with wild pig, a non‐ruminant generalist, and the sambar, a forest browser. Preferred plant biomass also fell sharply with increasing livestock density. Following the decline in livestock density in the livestock‐grazed area in 2002, the densities of gaur, chital and elephant increased by a factor of 57, five and two in the same area, respectively, whereas no changes were seen in the densities of wild pig and sambar or in the preferred plant biomass. Except for a decline in elephant density, the livestock‐free area did not show changes in wild herbivore densities. Given the considerable overlap in habitat and dietary preference/requirements between livestock and wild herbivores in the study area, it is suggested that the recovery of gaur, chital and elephant densities following the livestock decline represents their release from livestock‐mediated resource limitation. Synthesis and applications. These results indicate that resource competition may be intense between wild herbivores and grazing livestock, and if left unchecked could trigger declines of wild herbivores, particularly grazing ruminants and bulk feeders. These results also suggest that, where possible, interventions to reduce livestock grazing may rapidly benefit wild herbivores that have been competitively suppressed. This has important implications for the management of livestock grazing in India's wildlife reserves.