Introduction: The lower Syr Darya River Basin is an integral part of the Aral Sea Basin that is shared by four riparian countries. In Kazakhstan, the water is mainly used for agricultural purposes. However, the poor quality and insufficient quantity of water and the overall degradation of natural resources due to unsustainable management practices threaten the profitability of the sector. The situation is even worse for downstream users. Three alternative scenarios for sustainable water and land management were developed using the RIOS and SWAT models as decision support tools. The scenario that offered the highest water and land productivity was presented to farmers to assess their willingness to forgo their current practices and adopt proposed management practices. We introduce willingness to forego (WTF)—a qualitative approach and a variant of the concept of opportunity costs to look beyond hypothetical markets to trading current benefits for future returns. We also tap into literature on agricultural risk management to provide additional insight into farmers’ rationale behind their choices. Result: Generally, despite their stated preference to conserve ecosystem services, farmers’ actions were found to be inconsistent with the proposed sustainable management. WTF analysis revealed that farmers’ desire to maximize current benefits and more importantly to minimize future risks override all sustainability considerations. Their WTF current benefits mainly depended on their location along the canal and hence their access to water and land, overall cost of production, market conditions that informed their crop choices, and the cost of adopting recommended packages. While the results remain specific to this case, they are consistent with the literature that links farmers’ behaviors to ecological performances. Conclusions: The study highlights the limitations of decision support tools and other valuation approaches including willingness to pay (WTP) and willingness to accept (payment) (WTA), to capture the delicate trade-offs that need to be considered to ensure household food and income security and encourage adoption of sustainable ecosystem management practices. Adequate information on potential effects of proposed conservation measures on yield, markets and hence farm profits, and availability of other alternatives are critical in shaping farmers’ decisions.

INTRODUCTION: The lower Syr Darya River Basin is an integral part of the Aral Sea Basin that is shared by four riparian countries. In Kazakhstan, the water is mainly used for agricultural purposes. However, the poor quality and insufficient quantity of water and the overall degradation of natural resources due to unsustainable management practices threaten the profitability of the sector. The situation is even worse for downstream users. Three alternative scenarios for sustainable water and land management were developed using the RIOS and SWAT models as decision support tools. The scenario that offered the highest water and land productivity was presented to farmers to assess their willingness to forgo their current practices and adopt proposed management practices. We introduce willingness to forego (WTF)—a qualitative approach and a variant of the concept of opportunity costs to look beyond hypothetical markets to trading current benefits for future returns. We also tap into literature on agricultural risk management to provide additional insight into farmers’ rationale behind their choices. RESULT: Generally, despite their stated preference to conserve ecosystem services, farmers’ actions were found to be inconsistent with the proposed sustainable management. WTF analysis revealed that farmers’ desire to maximize current benefits and more importantly to minimize future risks override all sustainability considerations. Their WTF current benefits mainly depended on their location along the canal and hence their access to water and land, overall cost of production, market conditions that informed their crop choices, and the cost of adopting recommended packages. While the results remain specific to this case, they are consistent with the literature that links farmers’ behaviors to ecological performances. CONCLUSIONS: The study highlights the limitations of decision support tools and other valuation approaches including willingness to pay (WTP) and willingness to accept (payment) (WTA), to capture the delicate trade-offs that need to be considered to ensure household food and income security and encourage adoption of sustainable ecosystem management practices. Adequate information on potential effects of proposed conservation measures on yield, markets and hence farm profits, and availability of other alternatives are critical in shaping farmers’ decisions.

Valuation of ecosystem services is important for generating evidence for improved management of natural resources. Contingent Valuation (CV) is a common approach used to establish stakeholders’ stated preference by assessing their willingness to pay (WTP) or willingness to accept (WTA) monetary compensation for forgone services. This paper proposes another alternative - Willingness to Forego (WTF) – a variant of the concept of opportunity costs for soliciting stakeholders’ valuation of eco-system services, and to validate recommendations from two watershed models. The concept is tested in three villages located at the beginning, middle and tail end of the Turkistan canal in South Kazakhstan. Stakeholders’ WTF current benefits by changing their current management and use of irrigation water in lieu of optimal conservation measures proposed by the models were first established. Then stakeholders’ responses were analyzed from the perspective of agricultural risk-management, to understand drivers of their preferences. Despite their stated preference to conserve ecosystem services, agents were found to opt for options that offer maximum current benefits and minimum risks. Lack of information on potential effects of proposed conservation measures pushes farmers into the realm of uncertainty which influences their WTF. While the results remain specific to this case, they are consistent with literature that link farmers’ behaviors to ecological performances. The findings also present important basis for expanding the discussion on ecosystem valuation methods, and offers insight to decision makers to be cognizant of the need to maintain the delicate balance between ensuring current livelihoods and sustainable management of ecosystem services

Background: Grazing by livestock and cultivation have been considered as two important causes of soil erosion and nutrient export. However, there has been limited evidence that grazing or cultivation matters to soil erosion and nutrient export in Ethiopia. Hence, this study was conducted in the Galesa watershed in Ethiopia to examine the effects of grazing and cultivation on runoff, soil loss, and nutrient export. Daily values of runoff, soil erosion, and nutrient outflow were measured for three consecutive years following standard procedures. Independent t test was performed to check if the means of runoff, soil loss, and nutrient loss from grazing and cultivated lands were significantly different. Moreover, repeated analysis of variance (ANOVA) was used to test if mean values of runoff, soil loss, and nutrient export varied significantly over the study years. Results: Although the average annual runoff depth was 7.8% higher in grazing land (GL), soil erosion was significantly lower (39%) in GL as compared to cultivated land (CL). Similarly, sediment and runoff-associated annual losses of total nitrogen (N), available phosphorus (P), exchangeable potassium (K), and organic carbon (OC) were low in the GL treatments. Lowest losses of total N (9.30 kg ha-1 year-1 ), available P (0.83 kg ha-1 year-1 ), and exchangeable K (1.84 kg ha-1 year-1 ) were recorded in GL treatment. Likewise, lowest losses of sediment-associated total N (32.8 kg ha-1 year-1 ), available P (0.39 kg ha-1 year-1 ), exchangeable K (0.23 kg ha-1 year-1 ), and soil organic carbon (630 kg ha-1 year-1 ) were recorded from GL over the 3 years of experimentation. Conclusion: Our results indicate that cultivation increased soil erosion as compared to grazing. Although there were significant reductions in soil erosion and nutrient export from grazing lands compared with cultivated lands, the absolute losses were still high. This implies the need for grazing land management using appropriate physical and biological erosion control measures to increase productivity and reduce soil erosion as well as nutrient export.

BACKGROUND: Grazing by livestock and cultivation have been considered as two important causes of soil erosion and nutrient export. However, there has been limited evidence that grazing or cultivation matters to soil erosion and nutrient export in Ethiopia. Hence, this study was conducted in the Galesa watershed in Ethiopia to examine the effects of grazing and cultivation on runoff, soil loss, and nutrient export. Daily values of runoff, soil erosion, and nutrient outflow were measured for three consecutive years following standard procedures. Independent t test was performed to check if the means of runoff, soil loss, and nutrient loss from grazing and cultivated lands were significantly different. Moreover, repeated analysis of variance (ANOVA) was used to test if mean values of runoff, soil loss, and nutrient export varied significantly over the study years. RESULTS: Although the average annual runoff depth was 7.8% higher in grazing land (GL), soil erosion was significantly lower (39%) in GL as compared to cultivated land (CL). Similarly, sediment and runoff-associated annual losses of total nitrogen (N), available phosphorus (P), exchangeable potassium (K), and organic carbon (OC) were low in the GL treatments. Lowest losses of total N (9.30 kg ha⁻¹ year⁻¹), available P (0.83 kg ha⁻¹ year⁻¹), and exchangeable K (1.84 kg ha⁻¹ year⁻¹) were recorded in GL treatment. Likewise, lowest losses of sediment-associated total N (32.8 kg ha⁻¹ year⁻¹), available P (0.39 kg ha⁻¹ year⁻¹), exchangeable K (0.23 kg ha⁻¹ year⁻¹), and soil organic carbon (630 kg ha⁻¹ year⁻¹) were recorded from GL over the 3 years of experimentation. CONCLUSION: Our results indicate that cultivation increased soil erosion as compared to grazing. Although there were significant reductions in soil erosion and nutrient export from grazing lands compared with cultivated lands, the absolute losses were still high. This implies the need for grazing land management using appropriate physical and biological erosion control measures to increase productivity and reduce soil erosion as well as nutrient export.

Introduction: Ethiopia has made efforts to tackle the challenges of low crop and livestock productivity and degradation of land resources through various rural development strategies. However, increasing demands for food, animal feed, fuel, and income-generating activities are putting pressure on the land. In this paper, we describe the production pressure and competition between crop and livestock production, quantify rates of land-use/cover (LULC) changes, and examine driving forces and consequences of land conversion. Methods: The study was conducted in Gudo Beret watershed, North Shewa Zone of Amhara region, Ethiopia. It used a combination of methods including remote sensing, household interviews, field observations, focus group discussions, and key informant interviews. Supervised and unsupervised image classification methods were employed to map LULC classes for 31 years (1984–2016). Results: The results of satellite remote sensing revealed that 51% of the land in the study area was subject to accelerated land conversions. The household survey results indicated that feed resources and grain production pressures were 1.43 and 1.34 t ha−1 respectively. The observed annual changes in plantation and settlement areas were 2.6% and 2.9%. This was mainly at the expense of bushland and grazing land systems. Cropland increased (0.4% year−1) while grazing land reduced (3.5% year−1) under contrasting dynamics and competitive changes. An increase in human and livestock populations and farm expansion were major drivers of land conversion that adversely affected household livelihoods and the natural ecosystem. The consequences of these pressures resulted in a lack of animal feed, low crop-livestock productivity, and a reduction in natural vegetation coverage. Conclusions: We suggest that sustainable land resource management, more integrated crop-livestock production, and the use of productivity-enhancing technologies could play a role in managing competition for land resources.

INTRODUCTION: Ethiopia has made efforts to tackle the challenges of low crop and livestock productivity and degradation of land resources through various rural development strategies. However, increasing demands for food, animal feed, fuel, and income-generating activities are putting pressure on the land. In this paper, we describe the production pressure and competition between crop and livestock production, quantify rates of land-use/cover (LULC) changes, and examine driving forces and consequences of land conversion. METHODS: The study was conducted in Gudo Beret watershed, North Shewa Zone of Amhara region, Ethiopia. It used a combination of methods including remote sensing, household interviews, field observations, focus group discussions, and key informant interviews. Supervised and unsupervised image classification methods were employed to map LULC classes for 31 years (1984–2016). RESULTS: The results of satellite remote sensing revealed that 51% of the land in the study area was subject to accelerated land conversions. The household survey results indicated that feed resources and grain production pressures were 1.43 and 1.34 t ha⁻¹ respectively. The observed annual changes in plantation and settlement areas were 2.6% and 2.9%. This was mainly at the expense of bushland and grazing land systems. Cropland increased (0.4% year⁻¹) while grazing land reduced (3.5% year⁻¹) under contrasting dynamics and competitive changes. An increase in human and livestock populations and farm expansion were major drivers of land conversion that adversely affected household livelihoods and the natural ecosystem. The consequences of these pressures resulted in a lack of animal feed, low crop-livestock productivity, and a reduction in natural vegetation coverage. CONCLUSIONS: We suggest that sustainable land resource management, more integrated crop-livestock production, and the use of productivity-enhancing technologies could play a role in managing competition for land resources.

Land degradation through soil erosion by water is severe in the highlands of Ethiopia. In order to curb this problem, the government initiated sustainable land management interventions in different parts of the country since 2008, and in Geda watershed since 2012. However, the impacts of the interventions on soil properties were not assessed so far. Thus, this study investigated the impacts of sustainable land management interventions on selected soil properties in Geda watershed. Soil samples were collected from treated and untreated sub-watersheds at the upper and lower landscape positions, from cropland and grazing lands at two soil depths (0–15 cm and 15–30 cm). Selected soil physicochemical properties were assessed with respect to landscape position, land-use type, and soil depth in both treated and untreated sub-watersheds.Generally, most of the soil physicochemical properties differed greatly across sub-watersheds, land-use types, and soil depths. Clay, electrical conductivity, total N, available P, exchangeable K, and organic carbon were higher in the treated sub-watershed, whereas sand, silt, bulk density, and pH were higher in the untreated sub-watershed. The higher sand, silt, and bulk density could be attributed to erosion, while the higher pH could be due to the higher exchangeable Na in the untreated sub-watershed. Most of the selected soil chemical properties were not affected by landscape position, but land-use type affected available P and organic carbon with higher mean values at croplands than at grazing lands, which could be ascribed to the conservation structure and tillage of the soils in that conservation structures trap and accumulate transported organic materials from the upper slope, while tillage facilitates aeration and decomposition processes.Sustainable land management interventions improved soil physicochemical properties and brought a positive restoration of the soil ecosystem. Maintaining the soil conservation measures and enhancing community awareness about the benefits, coupled with management of livestock grazing are required to sustain best practices.

BACKGROUND: Land degradation through soil erosion by water is severe in the highlands of Ethiopia. In order to curb this problem, the government initiated sustainable land management interventions in different parts of the country since 2008, and in Geda watershed since 2012. However, the impacts of the interventions on soil properties were not assessed so far. Thus, this study investigated the impacts of sustainable land management interventions on selected soil properties in Geda watershed. Soil samples were collected from treated and untreated sub-watersheds at the upper and lower landscape positions, from cropland and grazing lands at two soil depths (0–15 cm and 15–30 cm). Selected soil physicochemical properties were assessed with respect to landscape position, land-use type, and soil depth in both treated and untreated sub-watersheds. RESULTS: Generally, most of the soil physicochemical properties differed greatly across sub-watersheds, land-use types, and soil depths. Clay, electrical conductivity, total N, available P, exchangeable K, and organic carbon were higher in the treated sub-watershed, whereas sand, silt, bulk density, and pH were higher in the untreated sub-watershed. The higher sand, silt, and bulk density could be attributed to erosion, while the higher pH could be due to the higher exchangeable Na in the untreated sub-watershed. Most of the selected soil chemical properties were not affected by landscape position, but land-use type affected available P and organic carbon with higher mean values at croplands than at grazing lands, which could be ascribed to the conservation structure and tillage of the soils in that conservation structures trap and accumulate transported organic materials from the upper slope, while tillage facilitates aeration and decomposition processes. CONCLUSION: Sustainable land management interventions improved soil physicochemical properties and brought a positive restoration of the soil ecosystem. Maintaining the soil conservation measures and enhancing community awareness about the benefits, coupled with management of livestock grazing are required to sustain best practices.

The effects of land use and land cover (LULC) on groundwater recharge and surface runoff and how these are affected by LULC changes are of interest for sustainable water resources management. However, there is limited quantitative evidence on how changes to LULC in semi-arid tropical and subtropical regions affect the subsurface components of the hydrologic cycle, particularly groundwater recharge. Effective water resource management in these regions requires conclusive evidence and understanding of the effects of LULC changes on groundwater recharge and surface runoff. We reviewed a total of 27 studies (2 modeling and 25 experimental), which reported on pre- and post land use change groundwater recharge or surface runoff magnitude, and thus allowed to quantify the response of groundwater recharge rates and runoff to LULC. Comparisons between initial and subsequent LULC indicate that forests have lower groundwater recharge rates and runoff than the other investigated land uses in semi-arid tropical/ subtropical regions. Restoration of bare land induces a decrease in groundwater recharge from 42% of precipitation to between 6 and 12% depending on the final LULC. If forests are cleared for rangelands, groundwater recharge increases by 7.8 ± 12.6%, while conversion to cropland or grassland results in increases of 3.4 ± 2.5 and 4.4 ± 3.3%, respectively. Rehabilitation of bare land to cropland results in surface runoff reductions of between 5.2 and 7.3%. The conversion of forest vegetation to managed LULC shows an increase in surface runoff from 1 to 14.1% depending on the final LULC. Surface runoff was reduced from 2.5 to 1.1% when grassland is converted to forest vegetation. While there is general consistency in the results from the selected case studies, we conclude that there are few experimental studies that have been conducted in tropical and subtropical semi-arid regions, despite that many people rely heavily on groundwater for their livelihoods. Therefore, there is an urgent need to increase the body of quantitative evidence given the pressure of growing human population and climate change on water resources in the region.

The effects of land use and land cover (LULC) on groundwater recharge and surface runoff and how these are affected by LULC changes are of interest for sustainable water resources management. However, there is limited quantitative evidence on how changes to LULC in semi-arid tropical and subtropical regions affect the subsurface components of the hydrologic cycle, particularly groundwater recharge. Effective water resource management in these regions requires conclusive evidence and understanding of the effects of LULC changes on groundwater recharge and surface runoff. We reviewed a total of 27 studies (2 modeling and 25 experimental), which reported on pre- and post land use change groundwater recharge or surface runoff magnitude, and thus allowed to quantify the response of groundwater recharge rates and runoff to LULC.Comparisons between initial and subsequent LULC indicate that forests have lower groundwater recharge rates and runoff than the other investigated land uses in semi-arid tropical/ subtropical regions. Restoration of bare land induces a decrease in groundwater recharge from 42% of precipitation to between 6 and 12% depending on the final LULC. If forests are cleared for rangelands, groundwater recharge increases by 7.8 ± 12.6%, while conversion to cropland or grassland results in increases of 3.4 ± 2.5 and 4.4 ± 3.3%, respectively.Rehabilitation of bare land to cropland results in surface runoff reductions of between 5.2 and 7.3%. The conversion of forest vegetation to managed LULC shows an increase in surface runoff from 1 to 14.1% depending on the final LULC. Surface runoff was reduced from 2.5 to 1.1% when grassland is converted to forest vegetation.While there is general consistency in the results from the selected case studies, we conclude that there are few experimental studies that have been conducted in tropical and subtropical semi-arid regions, despite that many people rely heavily on groundwater for their livelihoods. Therefore, there is an urgent need to increase the body of quantitative evidence given the pressure of growing human population and climate change on water resources in the region.

Sustainable land management interventions were introduced in Geda watershed in 2012 to reduce soil erosion, improve water infiltration, and increase plant-carbon inputs into the soil. This study explored the impact of the interventions on biomass production, carbon stock, and carbon sequestration. Stratified sampling was employed in the main and the dry seasons in the treated and untreated sub-watersheds that are found adjacent to each other. Above- and below-ground plant biomass, soil bulk density and organic carbon in 0–15- and 15–30-cm depths, and soil moisture content in 0–20- and 20–40-cm depths were collected from the crop, grazing, and tree lucerne plots. All analyses were performed based on standard procedures.Plant biomass production, carbon stock, and carbon sequestration varied highly significantly (P ≤ 0.001) among sub-watersheds, landscape positions, and land uses. Higher mean values were observed for treated sub-watershed, lower landscape position, and tree lucerne plot. The higher mean values in the lower landscape position of the treated sub-watershed were due to tree lucerne plantation. Similarly, topsoil (0–15 cm) carbon stock was statistically higher (P ≤ 0.001) in the treated sub-watershed and at tree lucerne plot (P ≤ 0.05). In addition, carbon stock by sub-surface soil (15–30 cm) was significantly higher (P ≤ 0.001) in the treated sub-watershed under crop and grazing lands but the higher value was in cropland and in the upper position. This could be due to the decomposition of organic materials from biomasses of crops and biological supporting measures (tree lucerne and Phalaris) facilitated by tillage. Six years of sustainable land management interventions led to the sequestration of 12.25, 7.77, and 13.5 Mg C ha−1 under cropland, tree lucerne, and grazing plots, respectively.Sustainable land management interventions revealed auspicious ecological impacts in Geda watershed in terms of improving plant biomass production, carbon stock, and correspondingly capturing higher carbon dioxide equivalent taking untreated sub-watershed as a baseline. Prohibition of free grazing was the key element of the intervention to reduce biomass export and increase carbon sequestration in the treated sub-watershed. Thus, sustaining tree lucerne plants as a conservation measure and the prohibition of free grazing practices are principally essential.

BACKGROUND: Sustainable land management interventions were introduced in Geda watershed in 2012 to reduce soil erosion, improve water infiltration, and increase plant-carbon inputs into the soil. This study explored the impact of the interventions on biomass production, carbon stock, and carbon sequestration. Stratified sampling was employed in the main and the dry seasons in the treated and untreated sub-watersheds that are found adjacent to each other. Above- and below-ground plant biomass, soil bulk density and organic carbon in 0–15- and 15–30-cm depths, and soil moisture content in 0–20- and 20–40-cm depths were collected from the crop, grazing, and tree lucerne plots. All analyses were performed based on standard procedures. RESULTS: Plant biomass production, carbon stock, and carbon sequestration varied highly significantly (P ≤ 0.001) among sub-watersheds, landscape positions, and land uses. Higher mean values were observed for treated sub-watershed, lower landscape position, and tree lucerne plot. The higher mean values in the lower landscape position of the treated sub-watershed were due to tree lucerne plantation. Similarly, topsoil (0–15 cm) carbon stock was statistically higher (P ≤ 0.001) in the treated sub-watershed and at tree lucerne plot (P ≤ 0.05). In addition, carbon stock by sub-surface soil (15–30 cm) was significantly higher (P ≤ 0.001) in the treated sub-watershed under crop and grazing lands but the higher value was in cropland and in the upper position. This could be due to the decomposition of organic materials from biomasses of crops and biological supporting measures (tree lucerne and Phalaris) facilitated by tillage. Six years of sustainable land management interventions led to the sequestration of 12.25, 7.77, and 13.5 Mg C ha⁻¹ under cropland, tree lucerne, and grazing plots, respectively. CONCLUSION: Sustainable land management interventions revealed auspicious ecological impacts in Geda watershed in terms of improving plant biomass production, carbon stock, and correspondingly capturing higher carbon dioxide equivalent taking untreated sub-watershed as a baseline. Prohibition of free grazing was the key element of the intervention to reduce biomass export and increase carbon sequestration in the treated sub-watershed. Thus, sustaining tree lucerne plants as a conservation measure and the prohibition of free grazing practices are principally essential.

Background: The savannah ecosystems of Sahel have experienced continuous and heavy grazing of livestock for centuries but still, their vegetation response to grazing pressure remains poorly understood. In this study, we analysed the herbaceous plant dynamics, measured by species diversity, composition, cover, and biomass in response to grazing pressure in the savannah ecosystems of Sahel. In Senegal, we selected four savannah sites represented with high, moderate, light and no grazing intensity levels. Transect survey methods were used for sampling the vegetation data within each of the sites. Species richness and composition were analysed using species accumulation curve and multivariate analyses. Furthermore, we used General Linear Models and a piecewise Structural Equation Model (pSEM) to examine the relationships between grazing intensity, vegetation cover, diversity and biomass. Results: The herbaceous species diversity and composition varied significantly among the different grazing intensity levels (p <0.001). The plant species composition shifted from the dominance of grass cover to the dominance of forb cover with increasing grazing pressure. Moreover, the attributes of species diversity, herbaceous biomass, and ground cover were higher on sites with low grazing than sites with high and moderate grazing intensity. Across all sites, species diversity was positively related to total biomass. The pSEM explained 37% of the variance in total biomass and revealed that grazing intensity negatively influenced total biomass both directly and indirectly through its negative influence on species diversity. Conclusions: Managing grazing intensity may lead to higher plant production and higher mixed forage establishment in the dryland savannah ecosystems. This information can be used to support land management strategies and promote sustainable grazing practices that balance the needs of livestock with the conservation of ecosystem health and biodiversity.

International audience | Background The savannah ecosystems of Sahel have experienced continuous and heavy grazing of livestock for centuries but still, their vegetation response to grazing pressure remains poorly understood. In this study, we analysed the herbaceous plant dynamics, measured by species diversity, composition, cover, and biomass in response to grazing pressure in the savannah ecosystems of Sahel. In Senegal, we selected four savannah sites represented with high, moderate, light and no grazing intensity levels. Transect survey methods were used for sampling the vegetation data within each of the sites. Species richness and composition were analysed using species accumulation curve and multivariate analyses. Furthermore, we used General Linear Models and a piecewise Structural Equation Model (pSEM) to examine the relationships between grazing intensity, vegetation cover, diversity and biomass. Results The herbaceous species diversity and composition varied significantly among the different grazing intensity levels ( p <0.001). The plant species composition shifted from the dominance of grass cover to the dominance of forb cover with increasing grazing pressure. Moreover, the attributes of species diversity, herbaceous biomass, and ground cover were higher on sites with low grazing than sites with high and moderate grazing intensity. Across all sites, species diversity was positively related to total biomass. The pSEM explained 37% of the variance in total biomass and revealed that grazing intensity negatively influenced total biomass both directly and indirectly through its negative influence on species diversity. Conclusions Managing grazing intensity may lead to higher plant production and higher mixed forage establishment in the dryland savannah ecosystems. This information can be used to support land management strategies and promote sustainable grazing practices that balance the needs of livestock with the conservation of ecosystem health and biodiversity.

Background The breakdown of dead organic matter is driven by a diverse array of organisms and is an important process increasingly impacted by a range of contaminants. While many studies have documented how contaminants affect food webs that are fueled by decaying plant litters, much less is known about how contaminants affect organisms that rely on dead animal material. Here, we begin to explore the effects of food contamination—using silver nanoparticles (AgNPs) as a model contaminant—on the carrion beetle Nicrophorus vespilloides that buries carcasses of small vertebrates in soils as food source and larval nursing grounds. Results Our data show that a single ingestion of a non-lethal dose of 1 μg mL−1 AgNPs by adult female beetles does not affect overall gut microbial activity but results in shifts in the gut microbial community composition towards pathogens including Alcaligenes, Morganella, and Pseudomonas. While no effects were observed in offspring clutch size, some reductions were visible in clutch weight, number of larvae, and number of eclosing pupae in exposed N. vespilloides in comparison with controls. Repeated ingestion of AgNPs over several weeks led to a decrease in survival of adult beetles, suggesting that more environmentally realistic exposure scenarios can directly affect the success of carcass-feeding animals. Conclusions Sub-lethal carcass contamination with a model pollutant can affect the gut microbial composition in female beetles and reduce offspring fitness. This encourages consideration of currently overlooked propagation routes of contaminants through necrophagous food webs and inherent consequences for ecological and evolutionary processes. | publishedVersion

BACKGROUND: The breakdown of dead organic matter is driven by a diverse array of organisms and is an important process increasingly impacted by a range of contaminants. While many studies have documented how contaminants affect food webs that are fueled by decaying plant litters, much less is known about how contaminants affect organisms that rely on dead animal material. Here, we begin to explore the effects of food contamination—using silver nanoparticles (AgNPs) as a model contaminant—on the carrion beetle Nicrophorus vespilloides that buries carcasses of small vertebrates in soils as food source and larval nursing grounds. RESULTS: Our data show that a single ingestion of a non-lethal dose of 1 μg mL⁻¹ AgNPs by adult female beetles does not affect overall gut microbial activity but results in shifts in the gut microbial community composition towards pathogens including Alcaligenes, Morganella, and Pseudomonas. While no effects were observed in offspring clutch size, some reductions were visible in clutch weight, number of larvae, and number of eclosing pupae in exposed N. vespilloides in comparison with controls. Repeated ingestion of AgNPs over several weeks led to a decrease in survival of adult beetles, suggesting that more environmentally realistic exposure scenarios can directly affect the success of carcass-feeding animals. CONCLUSIONS: Sub-lethal carcass contamination with a model pollutant can affect the gut microbial composition in female beetles and reduce offspring fitness. This encourages consideration of currently overlooked propagation routes of contaminants through necrophagous food webs and inherent consequences for ecological and evolutionary processes.