Maximizing tree carbon in croplands and grazing lands while sustaining yields.

BACKGROUND: Integrating trees into agricultural landscapes can provide climate mitigation and improves soil fertility, biodiversity habitat, water quality, water flow, and human health, but these benefits must be achieved without reducing agriculture yields. Prior estimates of carbon dioxide (CO2) removal potential from increasing tree cover in agriculture assumed a moderate level of woody biomass can be integrated without reducing agricultural production. Instead, we used a Delphi expert elicitation to estimate maximum tree covers for 53 regional cropping and grazing system categories while safeguarding agricultural yields. Comparing these values to baselines and applying spatially explicit tree carbon accumulation rates, we develop global maps of the additional CO2 removal potential of Tree Cover in Agriculture. We present here the first global spatially explicit datasets calibrated to regional grazing and croplands, estimating opportunities to increase tree cover without reducing yields, therefore avoiding a major cost barrier to restoration: the opportunity cost of CO2 removal at the expense of agriculture yields. RESULTS: The global estimated maximum technical CO2 removal potential is split between croplands (1.86 PgCO2 yr- 1) and grazing lands (1.45 PgCO2 yr- 1), with large variances. Tropical/subtropical biomes account for 54% of cropland (2.82 MgCO2 ha- 1 yr- 1, SD = 0.45) and 73% of grazing land potential (1.54 MgCO2 ha- 1 yr- 1, SD = 0.47). Potentials seem to be driven by two characteristics: the opportunity for increase in tree cover and bioclimatic factors affecting CO2 removal rates. CONCLUSIONS: We find that increasing tree cover in 2.6 billion hectares of agricultural landscapes may remove up to 3.3 billion tons of CO2 per year - more than the global annual emissions from cars. These Natural Climate Solutions could achieve the Bonn Challenge and add 793 million trees to agricultural landscapes. This is significant for global climate mitigation efforts because it represents a large, relatively inexpensive, additional CO2 removal opportunity that works within agricultural landscapes and has low economic and social barriers to rapid global scaling. There is an urgent need for policy and incentive systems to encourage the adoption of these practices.

Numerical classification of termite-mediated soils along toposequences and rangeland use influenced soil properties in southeast Ethiopia.

Despite termite-induced soil mixing, summarizing termite-affected soil horizons is difficult, while the lack of accurate information on the pedogenic processes featured by termite bioturbation, topography, and land use limits an effort to address land degradation. A study was therefore carried out to quantitatively classify the soils and describe them based on rangeland uses. Based on cluster analysis, five representative soil profiles were studied at different topographical positions. Soil samples were collected from mounds and adjacent soils under enclosure, cultivated, and open-grazing land at the summit and foot slope positions. Agglomerative clustering showed low Ca2+, CEC, pH, and Mg2+ that described cambic horizons formed Cambisols at the summit and back slope. Eluviation-illuviation processes formed Luvisols on the toe slope and foot slope, whereas clay and high CEC described argic horizons. High Ca2+, CEC, pH, and Mg2+ described calcic horizons that formed Calcisols on the bottom slope. Divisive clustering showed that soil properties varied slightly between Cambisols and Luvisols at different topographies. However, the Luvisols on the toe slope were differentiated from the soil on the foot slope by predominant pedogenetic clay formation and a distinctly increased CEC. Calcisols are placed in other clusters due to their distinct properties. Agglomerative clustering reflected pedogenic processes and differentiated diagnostic horizons, while divisive clustering matched WRB classification. The results of this study also showed that termite-mediated soil properties were dictated by rangeland use, and pedogenesis was more noticeable on open-grazing land than on enclosure or cultivated land.

Evaluating the Ecological Footprint of Landfills: A Framework and Case Study of Fargo, North Dakota.

There is growing interest in better understanding the environmental impacts of landfills and optimizing their operation. Accordingly, we developed a holistic framework to calculate a landfill's Ecological Footprint (EF) and applied that to the Fargo, North Dakota, landfill. Parallelly, the carbon footprint and biocapacity of the landfill were calculated. We calculated the EF for six scenarios (i.e., cropland, grazing land, marine land, inland fishing ground, forest land, and built land as land types) and six operational strategies typical for landfills. Operational strategies were selected based on the variations of landfill equipment, the gas collection system, efficiency, the occurrence of fugitive emissions, and flaring. The annual EF values range from 124 to 213,717 global hectares depending on land type and operational strategy. Carbon footprints constituted 28.01-99.98% of total EF, mainly driven by fugitive emissions and landfill equipment. For example, each percent increase in Fargo landfill's fugitive emissions caused the carbon footprint to rise by 2130 global hectares (4460 tons CO2e). While the landfill has biocapacity as grazing grass in open spaces, it remains unused/inaccessible. By leveraging the EF framework for landfills, operators can identify the primary elements contributing to a landfill's environmental impact, thereby minimizing it.

Assessing the spatial effects of economic freedom on forest-products, grazing-land, and cropland footprints: The case of Asia-Pacific countries.

The literature has shown that economic freedom yields higher economic growth. However, the nexus between economic freedom and the environment in a world of spatial dependency is unclear. Using data from a panel of seventeen Asia-Pacific countries from 2000 to 2017, we investigate the direct and spillover effects of economic freedom (as measured by the annual indexes developed by the Heritage Foundation) and other variables on the ecological footprint of three land-cover types: cropland, forest products, and grazing land. Diagnostic tests confirm the existence of spatial-interaction effects in forest products and grazing land but reject it for cropland. Using a spatial Durbin panel model, we find that the intensity of energy use has a significant impact on the environmental footprint of all resource types. We also confirm the environmental Kuznets curve hypothesis for forest products and grazing land but not cropland. Unlike previous researchers, we find cropland footprints are unaffected by natural resource rents. We also find that the tax burden is the only economic freedom indicator with a positive and significant impact on all three environmental footprints. Our findings suggest that more investment freedom reduces environmental pressure on cropland and forest-products footprints but has a nonsignificant effect on the grazing-land footprint. Further, financial freedom reduces the forest-products footprint and increases the grazing-land footprint. Property rights, the tax burden, and business freedom increase environmental pressure while government spending lessens grazing land's ecological footprint. Our indirect and overall impact analyses suggest that all types of economic freedom reduce environmental strain in our panel. This research points to the importance of enacting environmental regulations in a way that guarantees ecological sustainability and economic development.

Impact of biological nitrogen fixation and livestock management on the manure transfer from grazing land in mixed farming systems.

Soil fertility in mixed farming systems relies on the manure produced by livestock and its recycling in the entire system. In the particular case of crop-livestock system with grazing area, the proper functioning of the system also depends on the presence of nitrogen-fixing plants in the area where livestock grazes (the grazing land). In this paper, we study the impact of biological nitrogen fixation (BNF) and livestock management on the flux of manure exported outside the grazing land. We address this issue using a modeling approach. We consider a plant-soil model composed of a set of nonlinear ordinary differential equations that represents the grazing land. We assume that the manure produced by the grazing livestock can be partially exported as a fertilizer outside of this area. Through the mathematical analysis of the model, and analytical and numerical optimization, we then determine the optimal livestock management in terms of grazing rate and manure recycling percentage that lead to the maximal flux of exported manure. We focus more precisely on the role of nitrogen-fixing plants and their impact on the optimal livestock management. When grazing rate is high and the capacity of plants to fix nitrogen is important, we showed that it is necessary to recycle some of the manure produced by the livestock in the grazing land to maximize the flux of exported manure. On the contrary, if we can optimize both the grazing rate and the manure recycling percentage, then it is better to transfer all the produced manure and to adapt the grazing rate accordingly to minimize nitrogen losses from the soil. Finally, to maximize the flux of exported manure, it is also necessary to bring the system to a state in which the plants fix nitrogen. In this way, we can benefit from the nitrogen fixation which provides an additional input of nitrogen in the system.

Impact of exclosures on woody species diversity in degraded lands: the case of Lemo in Southwestern Ethiopia.

Exclosures are popularly applied to rehabilitate degraded lands and to gradually restore the productive potential of the land in the long term. This study was conducted to examine the impact of removing human and livestock interference from a degraded land to allow natural recuperation for extended period of years. The aim was to assess the trend of changes in the composition, diversity and structure of the woody component of the vegetation within the exclosures. Degraded lands with different years of exclosure were compared with adjacent open grazing lands under similar environmental conditions. A Systematic transect sampling method was employed to collect vegetation data in sampling quadrat plots, each with a size of 20 m × 20 m, evenly distributed along parallel transect lines. All the woody plant species in each plot were identified and measured for DBH and height. The species diversity and density were analyzed using standard indices. The structural pattern and regeneration status of the woody vegetation was described using size class distribution plots. The findings showed that the woody vegetation composition significantly varied between exclosures and open grazing land. There was significantly (P < 0.05) higher diversity, richness and stand density of the woody species in the exclosures than in the open grazing lands. The size class distribution of the DBH and height of the recorded species exhibited an inverted "J" shape pattern suggesting a healthy regeneration status of the important species, while the distribution pattern in the open grazing lands revealed irregular and less interpretable pattern. This study evidently showed exclosures can successfully contribute to biodiversity restoration in highly degraded lands, perhaps due to improvements in the important micro-climate conditions such as moisture and organic matter.

Estimating carrying capacity and stocking rates of rangelands in Harshin District, Eastern Somali Region, Ethiopia.

We conducted a quantitative assessment of forage biomass in Harshin district to determine its annual productive potential, carrying capacity, and stocking rates. The dominant Land Use and Land Cover include woodland (35.5%), shrubs (28.3%), grassland (10.6%), and bare land (25.5%). The region has browse-rich shrubland that is edible to dromedary and goats, as well as massive grassland plains for sheep and cattle. The interannual rainfall variation is 16.5% which implies that the rangeland is a subsistence equilibrium system. The range of forage production is between 105 and 2,310 kg/ha, whereas the average productivity of the district is 742.6 kg/ha. The result indicates that the average carrying capacity of the district is 0.3 TLU ha-1 year-1 (4.9 ha TLU-1 year-1) while the existing stocking rate is 5.4 TLU ha-1 year-1 (0.18 ha TLU-1 year-1). This implies that the grazing intensity in the district is much higher than its carrying capacity (recommended rate), which has seen overstocking or grazing pressure excesses of 5.1 TLU/ha (7.2 cattle/ha). Thus, it clearly signals the risk of overgrazing in the district. If this trend continues, the grazing will not be sustainable and there will be shortage of forage as well as expansion of land degradation (due to overgrazing) in the near future.

Carbon sequestration and soil restoration potential of grazing lands under exclosure management in a semi-arid environment of northern Ethiopia.

Exclosures are used to regenerate native vegetation as a way to reduce soil erosion, increase rain water infiltration and provide fodder and woody biomass in degraded grazing lands. Therefore, this study assessed the impact of grazing exclosure on carbon sequestration and soil nutrients under 5 and 10 years of grazing exclosures and freely grazed areas in Tigray, northern Ethiopia. Carbon stocks and soil nutrients increased with increasing grazing exclusion. However, open grazing lands and 5 years of grazing exclosure did not differ in above- and belowground carbon stocks. Moreover, 10 years of grazing exclosure had a higher (p < 0.01) grass, herb and litter carbon stocks compared to 5 years exclosure and open grazing lands. The total carbon stock was higher for 10 years exclosure (75.65 t C ha-1) than the 5 years exclosure (55.06 t C ha-1) and in open grazing areas (51.98 t C ha-1). Grazing lands closed for 10 years had a higher SOC, organic matter, total N, available P, and exchangeable K + and Na + compared to 5 year's exclosure and open grazing lands. Therefore, establishment of grazing exclosures had a positive effect in restoring degraded grazing lands, thus improving carbon sequestration potentials and soil nutrients.

Interannual variation in grassland net ecosystem productivity and its coupling relation to climatic factors in China.

Grassland, as an important part of land cover, plays an important role in the global carbon cycle and carbon balance. Net ecosystem productivity (NEP) is a key indicator of the carbon cycle process and an important factor in assessing ecosystem security and maintaining ecosystem balance. In this paper, Boreal Ecosystem Productivity Simulator (BEPS) combining meteorological data, leaf area index, and land cover type data were used to simulate the grassland NEP of China from 1979 to 2008. This model was also used to analyze the responses to changes in climate factors, interannual variation in carbon conversion efficiency, drought stress coefficient, and water use efficiency of grassland in China. Results showed that from 1979 to 2008, the mean annual grassland NEP was 13.6 g C/m2 with weak carbon sinks. The grassland NEP distribution increased from northwest to southeast across China. Regions with NEP of > 0 (C sink) accounted for 73.1% of the total grassland area of China. The total C sequestration reached 26.6 Tg yearly, and grassland NEP was positive from 1979 to 2008. The annual changing characteristics were analyzed. Grassland NEP was positive with carbon sink from June to September, which was negative with carbon source in the remaining months. The carbon conversion efficiency and water use efficiency of the grassland increased significantly within 30 years. NEP showed positive correlation with precipitation (accounting for 74.2% of the total grassland area was positively correlated) but weakly positive correlation with temperature (50.2% of the case). Furthermore, significant positive correlation was found between grassland NEP and precipitation, especially in northeastern and central Inner Mongolia, northern Tianshan of Xinjiang, southwestern Tibet, and southern Qinghai Lake.

Arsenic distribution in a pasture area impacted by past mining activities.

Former mine exploitations entail a serious threat to surrounding ecosystems as after closure of mining activities their unmanaged wastes can be a continuous source of toxic trace elements. Quite often these mine sites are found within agricultural farming areas, involving serious hazards as regards product (feed/food) quality. In this work a grazing land impacted by the abandoned mine exploitation of an arsenical deposit was studied so as to evaluate the fate of arsenic (As) and other trace elements and the potential risks involved. With this aim, profile soil samples (0-50cm) and pasture plant species (Agrostis truncatula, Holcus annus and Leontodon longirostris) were collected at different distances (0-100m) from the mine waste dump and analyzed for their trace element content and distribution. Likewise, plant trace element accumulation from impacted grazing soils and plant trace element translocation were assessed. The exposure of livestock grazing animals to As was also evaluated, establishing its acceptability regarding food safety and animal health. International soil guideline values for As in grazing land soils (50mgkg-1) resulted greatly exceeded (up to about 20-fold) in the studied mining-affected soils. Moreover, As showed a high mobilization potential under circumstances such as phosphate application or establishment of reducing conditions. Arsenic exhibited relatively high translocation factor (TF) values (up to 0.32-0.89) in pasture plant species, reaching unsafe concentrations in their above-ground tissues (up to 32.9, 16.9 and 9.0mgkg-1 in Agrostis truncatula, Leontodon longirostris and Holcus annus, respectively). Such concentrations represent an elevated risk of As transfer to the high trophic-chain levels as established by international legislation. The limited fraction of arsenite found in plant roots should play an important role in the relatively high As root-to-shoot translocation shown by these plant species. Both soil ingestion and pasture intake resulted important entrance pathways of As into livestock animals, showing quite close contribution levels. The cow acceptable daily intake (ADI) of As regarding food safety was surpassed in some locations of the study area when the species Agrostis truncatula was considered as the only pasture feed. Restrictions in the grazing use of lands with considerable As contents where this plant was the predominant pasture species should be established in order to preserve food quality. Therefore, the exposure of livestock animals to As via both soil ingestion and pasture consumption should be taken into account to establish the suitability of mining-impacted areas for gazing.

Social capital, collective action, and communal grazing lands in Uganda.

Recent scholars have found that collective action can be harnessed to sustainably manage common property, contrary to longstanding hypotheses that without effective external regulation community members will exploit communal resources. Researchers have also found that social capital, in addition to biophysical conditions and community attributes, is an important element of successful collective action. However, few studies exploring this topic have specifically examined communal grazing land, which is a critical component of rural livelihoods in many parts of the developing world. To address this gap, we explore the role that collective action plays in maintaining communal grazing lands through bridging, bonding, and linking social capital. In cases where the community does have communal grazing lands, we also explore the role of social capital in determining the condition of the land and the inclusiveness of access. Our analyses draw upon a community-level dataset composed of Uganda RePEAT survey data linked with high resolution gridded socio-environmental data. We observe that strong community bonds are associated with higher odds of successful collective action. However, increased links to external market forces may decrease the odds of successful collective action. These findings provide additional evidence for the complex relationship between social capital, collective action, and common property natural resource management.

Model-based analysis of the environmental impacts of grazing management on Eastern Mediterranean ecosystems in Jordan.

Eastern Mediterranean ecosystems are prone to desertification when under grazing pressure. Therefore, management of grazing intensity plays a crucial role to avoid or to diminish land degradation and to sustain both livelihoods and ecosystem functioning. The dynamic land-use model LandSHIFT was applied to a case study on the country level for Jordan. The impacts of different stocking densities on the environment were assessed through a set of simulation experiments for various combinations of climate input and assumptions about the development of livestock numbers. Indicators used for the analysis include a set of landscape metrics to account for habitat fragmentation and the "Human Appropriation of Net Primary Production" (HANPP), i.e., the difference between the amount of net primary production (NPP) that would be available in a natural ecosystem and the amount of NPP that remains under human management. Additionally, the potential of the economic valuation of ecosystem services, including landscape and grazing services, as an analysis concept was explored. We found that lower management intensities had a positive effect on HANPP but at the same time resulted in a strong increase of grazing area. This effect was even more pronounced under climate change due to a predominantly negative effect on the biomass productivity of grazing land. Also Landscape metrics tend to indicate decreasing habitat fragmentation as a consequence of lower grazing pressure. The valuation of ecosystem services revealed that low grazing intensity can lead to a comparatively higher economic value on the country level average. The results from our study underline the importance of considering grazing management as an important factor to manage dry-land ecosystems in a sustainable manner.