Widespread and major losses in multiple ecosystem services as a result of agricultural expansion in the Argentine Chaco

Moving from ecological impacts to social vulnerability in data-scarce places

Managers need to trace social impacts and vulnerability caused by environmental change all the way to its driving forces to target key system components for intervention. However, most available scientific evidence deals with either the ecological impacts of direct drivers or the value of ecosystem benefits to people. Our matrix-based tool combines these types of evidence to make environmental management problems traceable through a structured yet flexible procedure. The tool consists of a series of matrices that sequentially link direct drivers of environmental change, landscapes, ecological conditions, benefits to people, and stakeholder types. Qualitative matrices result from the integration and synthesis of available evidence from literature reviews, and where data is scarce, these are used to elicit quantitative scores from expert opinion. Expert scoring of links and multiplication of matrices allow for estimating the impacts of each driver of environmental change on each stakeholder type and using this information as input to assess stakeholders' vulnerability through impact-influence diagrams. Applying the tool to the Argentine Gran Chaco, a globally threatened ecoregion, yielded a transparent and reliable picture of this data-scarce place, with important management implications. Tracing stakeholder impacts back to direct drivers confirmed that further encroachment of cleared areas around indigenous lands will increase the vulnerability of this social group. Also, assessing confidence levels for every social-ecological link suggested that incentivizing peasant farmers to restore natural forage supply represents a management opportunity to reverse degradation. Our tool makes interdisciplinary frameworks of linked ecological and social systems operational so managers can use the best available knowledge of a place and account for uncertainty to make environmental management decisions.

Spatial patterns of nutrients balance of major crops in Argentina

Argentina has a long tradition of agricultural systems that use few amounts of fertilizers. However, the crop nutrient balance remains unknown throughout the country. In this study, we estimated the nitrogen (N), phosphorus (P) and sulfur (S) balance at national and subnational scale of the six major grain crops: soybean, maize, wheat, sunflower, barley and sorghum. We found a negative spatio-temporal NPS balance with an annual average deficit of -22.4 kg ha^-1 year^-1 for N, -6.9 kg ha^-1 year^-1 for P and -2.1 kg ha^-1 year^-1 for S. Considering the whole agricultural area analyzed, the balance represented a mean annual negative net outflow of 612 thousand tons (kT) of N, 166 kT of P and 58 kT of S. The nutrient balance was not homogeneous across the country, with significant differences among the three major productive regions: i) the Pampean nucleus region (-32.2, -8.5, -2.92 kg ha^-1 year^-1, for N, P and S respectively) ii) the non-nucleus Pampean region (-14.3, -3.7, -2.03 kg ha^-1 year^-1 for N, P and S respectively), and iii) extra-Pampean region (-22.4, -6.3, -2.13 kg ha^-1 year^-1 for N, P and S respectively). Remarkably, despite having the highest N and P application rate, the Pampean nucleus region has the largest deficit of the analyzed nutrients. Soybean was the main driver of the nutrient mining in the country, accounting for 62 % of the NPS deficits at national scale (-418 kT N year^-1, -120 kT P year^-1 and -35 kT S year^-1). Our findings suggest that the current fertilization practices applied to the major extensive crops in Argentina are far from being sufficient to supply the nutrients they demand, even cultivating soybean that is a N-fixing crop. These results highlight that Argentine main crops' high productivity is reached at the expense of soil nutrient depletion.

Quality of the surface water of a basin affected by the expansion of the agricultural frontier over the native forest in the Argentine Espinal region

Land use changes have led to the degradation of multiple ecosystem services and affected the quality of aquatic ecosystems. The aims of this study were (i) to assess the expansion of the agricultural border over the native forest of an Argentinean stream basin and (ii) to characterize the surface water quality, considering physicochemical parameters, and pesticide concentrations. The agricultural frontier expansion was estimated through the analysis of satellite image coverage. Samples of surface water were taken bimonthly for 2 years. The native forest cover decreased from 72% in 1987 to 60% in 2017 due to the sustained increase in agricultural activities. In surface water, the concentrations of cations decreased: Na > Ca > K > Mg, whereas those of anions decreased: HCO₃ >  > Cl > SO₄ > PO₄. The 84 surface water samples analyzed revealed 25 pesticides, including herbicides (44%), insecticides (28%), and fungicides (28%). Herbicides were detected in more than 60% of the samples. 2,4-D, atrazine, cyproconazole, diazinon, glyphosate, AMPA, and metolachlor were detected in all the study sites and sometimes, 2,4-D, atrazine, dicamba, and metolachlor concentrations exceeded the guideline levels. The high sampling frequency of this study and the two annual cycles of crops in the basin enabled sensing of pesticide molecules and concentrations that had not been previously detected, indicating diffuse contamination. These findings signal an emergent challenge on the Espinal agro-ecosystem integrity due to changes in land use.

Identifying priority regions and territorial planning strategies for conserving native vegetation in the Cerrado (Brazil) under different scenarios of land use changes

The Cerrado biome covers approximately 20% of Brazil and it is crucial for the Water, Food, Energy, and Ecosystems (WFEE) nexus. Thus, in recent years, large areas of the undisturbed Cerrado have been converted into farmland. In this biome, according to the Brazilian Forest Code, farmers need to keep 20% of native vegetation (Legal Reserves - LRs). By exploring combined and isolated impacts of different scenarios of LR and Protected area (PA) arrangements, this study evaluated the importance of complementarity between LR compliance and the amount of PAs (including Conservation Units - CUs and Indigenous Lands - ILs) to reduce deforestation and conserve native vegetation in the Cerrado. Seven scenarios were investigated: a scenario that considers the current PA and the LR values foreseen in the Native Vegetation Protection Law - NVPL; three scenarios focused on production; and three focused on conservation. Considering the trend of the current scenario, the estimated loss of native vegetation will be 30% (30.6 million ha) by 2070. According to the model simulations, for two periods (2050 and 2070), the LR Elimination scenario (LRE) would cause a greater loss of native vegetation than the PA Elimination (PAE), and as expected, the exclusion of both (PALRE) would provide a greater loss of native vegetation. Native vegetation is concentrated mainly on agricultural properties. Taking our conservation-oriented scenarios as an example of conservation strategies, if there were no financial, practical, political, social or personal constraints, there is no doubt that the CPALRI scenario (Creation of Protected Areas and Legal Reserve Increase) is the best trajectory for conserving biodiversity. Therefore, private properties, through LRs, are essential for efficient planning of land use/cover as they ensure security in the WFEE nexus. The resulting projected scenarios are important to help decision makers in territorial planning and how to arbitrate territorial demands aiming at the rational use of the natural resources of the Cerrado.

Agricultural expansion and the ecological marginalization of forest-dependent people

Agricultural expansion into subtropical and tropical forests causes major environmental damage, but its wider social impacts often remain hidden. Forest-dependent smallholders are particularly strongly impacted, as they crucially rely on forest resources, are typically poor, and often lack institutional support. Our goal was to assess forest-smallholder dynamics in relation to expanding commodity agriculture. Using high-resolution satellite images across the entire South American Gran Chaco, a global deforestation hotspot, we digitize individual forest-smallholder homesteads (n = 23,954) and track their dynamics between 1985 and 2015. Using a Bayesian model, we estimate 28,125 homesteads in 1985 and show that forest smallholders occupy much larger forest areas (>45% of all Chaco forests) than commonly appreciated and increasingly come into conflict with expanding commodity agriculture (18% of homesteads disappeared; n = 5,053). Importantly, we demonstrate an increasing ecological marginalization of forest smallholders, including a substantial forest resource base loss in all Chaco countries and an increasing confinement to drier regions (Argentina and Bolivia) and less accessible regions (Bolivia). Our transferable and scalable methodology puts forest smallholders on the map and can help to uncover the land-use conflicts at play in many deforestation frontiers across the globe. Such knowledge is essential to inform policies aimed at sustainable land use and supply chains.

Forest strips increase connectivity and modify forests' functioning in a deforestation hotspot

Land use changes are occurring with unprecedented magnitude and intensity, imposing global impacts on ecosystem services (ES) and biodiversity. While the impacts of land use changes are increasingly recognized, understanding how landscape connectivity is related to ecosystem functioning is lacking. In the Argentinian Dry Chaco, deforestation increased forest fragmentation but strips of native forest (linear remnants) were usually left after clearings. Although the number of ecological studies on forest strips has increased, their contribution to forest connectivity and functioning has not been assessed. We evaluated the contribution of forest strips to forest connectivity and estimated its effect on forests' functioning considering low, moderate, and high species' dispersal abilities in our estimation. The effects of forest strip connectivity contribution to the forests' Ecosystem Services Supply Index (Forests' ESSI) was also analyzed. Forest strips contributed on average 6% and up to 40% to forest connectivity for moderate dispersal abilities, while low and high dispersals presented low values in almost all cases. The connectivity contribution was highest (between 15 and 40%) and variable for moderate dispersal abilities in landscapes with between 25 and 35% of forest cover. High connectivity contribution was generally achieved for low and moderate dispersals when forest strips conformed a network among forest patches. Forest strip connectivity significantly increased the forests' ESSI (between 1.3 and 2.4% per unit of connectivity contribution) and its effect was higher in comparison to forest amount and fragmentation. This study provides insights for planning the location of forest strips and forest remnants in agricultural landscapes, thus increasing forest connectivity for enhancing ecosystem functioning.

Limited Economic-Ecological Trade-Offs in a Shifting Agricultural Landscape: A Case Study From Kern County, California

Increasing global food production and livelihoods while maintaining ecosystem health will require significant changes in the way existing farming landscapes are managed. To this end, developing a systemic understanding of the economic and ecological impacts of different cropping systems, and identifying trade-offs and synergies between them, is crucial to inform decision-making for policy makers and landowners. Here, we investigate the impacts of agricultural land-use change for 15 distinct crops in Kern County, California, by looking at spatial and temporal changes in ecosystem indicators. We focus our analysis on three agricultural ecosystem pressures (water use, soil erosion, and pesticide use) and three agricultural ecosystem services (profits, calorie production, and C sequestration). Between 2002 and 2018, agriculture in Kern County underwent a shift from annual row crop to nut tree crop production. At the landscape-scale, we found high increases in ecosystem service provision (total profits, calorie production, and annual C sequestration increased by 105, 29, and 37%, respectively), coupled with smaller changes in ecosystem pressures (total soil erosion and evapotranspiration increased by 10 and 5%, respectively, and total pesticide use declined by 4%). We identified no salient trade-offs or synergies among crops. Our results illustrate that in the highly productive agricultural hotspot of Kern County, a combination of changes in land-cover allocation or land-use efficiency may have mitigated stronger negative environmental impacts following a broad shift from annual to perennial crops.