Improving carbon sequestration estimation through accounting carbon stored in grassland soil.

Based on international guidelines, the elaboration of national carbon (C) budgets in many countries has tended to set aside the capacity of grazing lands to sequester C as soil organic carbon (SOC). A widely applied simple method assumes a steady state for SOC stocks in grasslands and a long-term equilibrium between annual C gains and losses. This article presents a theoretical method based on the annual conversion of belowground biomass into SOC to include the capacity of grazing-land soils to sequester C in greenhouse gases (GHG) calculations. Average figures from both methods can be combined with land-use/land-cover data to reassess the net C sequestration of the rural sector from a country. The results of said method were validated with empirical values based on peer-reviewed literature that provided annual data on SOC sequestration. This methodology offers important differences over pre-existing GHG landscape approach calculation methods: •improves the estimation about the capacity of grazing-land soils to sequester C assuming these lands are not in a steady state and•counts C gains when considering that grazing lands are managed at low livestock densities.

Reassessing the role of grazing lands in carbon-balance estimations: Meta-analysis and review.

Assuming a steady state between carbon (C) gains and losses, greenhouse gases (GHG) inventories that follow a widely used simplified procedure (IPCC Tier 1) tend to underestimate the capacity of soils in grazing-land to sequester C. In this study we compared the C balance reported by (i) national inventories that followed the simplified method (Tier 1) of IPCC (1996/2006), with (ii) an alternative estimation derived from the meta-analysis of science-based, peer-reviewed data. We used the global databases (i) EDGAR 4.2 to get data on GHG emissions due to land conversion and livestock/crop production, and (ii) HYDE 3.1 to obtain historical series on land-use/land cover (LULC). In terms of sequestration, our study was focused on C storage as soil organic carbon (SOC) in rural lands of four countries (Argentina, Brazil, Paraguay and Uruguay) within the so-called MERCOSUR region. Supported by a large body of scientific evidence, we hypothesized that C gains and losses in grazing lands are not in balance and that C gains tend to be higher than C losses at low livestock densities. We applied a two-way procedure to test our hypothesis: i) a theoretical one based on the annual conversion of belowground biomass into SOC; and ii) an empirical one supported by peer-reviewed data on SOC sequestration. Average figures from both methods were combined with LULC data to reassess the net C balance in the study countries. Our results show that grazing lands generate C surpluses that could not only offset rural emissions, but could also partially or totally offset the emissions of non-rural sectors. The potential of grazing lands to sequester and store soil C should be reconsidered in order to improve assessments in future GHG inventory reports.

Partition of some key regulating services in terrestrial ecosystems: Meta-analysis and review.

Our knowledge about the functional foundations of ecosystem service (ES) provision is still limited and more research is needed to elucidate key functional mechanisms. Using a simplified eco-hydrological scheme, in this work we analyzed how land-use decisions modify the partition of some essential regulatory ES by altering basic relationships between biomass stocks and water flows. A comprehensive meta-analysis and review was conducted based on global, regional and local data from peer-reviewed publications. We analyzed five datasets comprising 1348 studies and 3948 records on precipitation (PPT), aboveground biomass (AGB), AGB change, evapotranspiration (ET), water yield (WY), WY change, runoff (R) and infiltration (I). The conceptual framework was focused on ES that are associated with the ecological functions (e.g., intermediate ES) of ET, WY, R and I. ES included soil protection, carbon sequestration, local climate regulation, water-flow regulation and water recharge. To address the problem of data normality, the analysis included both parametric and non-parametric regression analysis. Results demonstrate that PPT is a first-order biophysical factor that controls ES release at the broader scales. At decreasing scales, ES are partitioned as result of PPT interactions with other biophysical and anthropogenic factors. At intermediate scales, land-use change interacts with PPT modifying ES partition as it the case of afforestation in dry regions, where ET and climate regulation may be enhanced at the expense of R and water-flow regulation. At smaller scales, site-specific conditions such as topography interact with PPT and AGB displaying different ES partition formats. The probable implications of future land-use and climate change on some key ES production and partition are discussed.

A rapid method for assessing the environmental performance of commercial farms in the Pampas of Argentina.

The generation of reliable updated information is critical to support the harmonization of socio-economic and environmental issues in a context of sustainable development. The agro-environmental assessment and management of agricultural systems often relies on indicators that are necessary to make sound decisions. This work aims to provide an approach to (a) assess the environmental performance of commercial farms in the Pampas of Argentina, and (b) propose a methodological framework to calculate environmental indicators that can rapidly be applied to practical farming. 120 commercial farms scattered across the Pampas were analyzed in this study during 2002 and 2003. Eleven basic indicators were identified and calculation methods described. Such indicators were fossil energy (FE) use, FE use efficiency, nitrogen (N) balance, phosphorus (P) balance, N contamination risk, P contamination risk, pesticide contamination risk, soil erosion risk, habitat intervention, changes in soil carbon stock, and balance of greenhouse gases. A model named Agro-Eco-Index was developed on a Microsoft-Excel support to incorporate on-farm collected data and facilitate the calculation of indicators by users. Different procedures were applied to validate the model and present the results to the users. Regression models (based on linear and non-linear models) were used to validate the comparative performance of the study farms across the Pampas. An environmental dashboard was provided to represent in a graphical way the behavior of farms. The method provides a tool to discriminate environmentally friendly farms from those that do not pay enough attention to environmental issues. Our procedure might be useful for implementing an ecological certification system to reward a good environmental behavior in society (e.g., through tax benefits) and generate a commercial advantage (e.g., through the allocation of green labels) for committed farmers.

Environmental assessment of agriculture at a regional scale in the Pampas of Argentina.

Governments need good information to design policies. However, in the Argentine Pampas there are neither sufficient knowledge on environmental issues, nor clear perception of environmental alterations across space and time. The general objective of this work was to provide decision makers with a scientifically sound set of indicators aiming at the assessment of current status and future trends in the rural environment of this sensitive region. As driving criteria to select indicators, we assumed that they had to be sound, simple to calculate, easy to understand, and easily applicable by decision makers. They are related closely to significant ecological structures and functions. Twelve basic indicators were identified: (1) land use, (2) fossil energy use, (3) fossil energy use efficiency, (4) nitrogen (N) balance, (5) phosphorus (P) balance, (6) nitrogen contamination risk, (7) phosphorus contamination risk, (8) pesticide contamination, (9) soil erosion risk, (10) habitat intervention, (11) changes in soil carbon stock, and (12) balance of greenhouse gases. Indicators were geographically referenced using a geographic information system (GIS). The strength of this study is not in the absolute value of environmental indicators, but rather in the conceptualization of indicator and the identification of changing patterns, gradients and trends in space and time. According to our results, we can not definitely say that agriculture in the Pampas, as a whole, tends to be sustainable or not. While some indicators tend to improve, others keep stable, and the rest worsen. The relative importance among indicators must also be considered. The indicators that showed a negative net change are key to the identification of critical problems that will require special attention in the close future.