Diagnosis of the Accelerated Soil Erosion in São Paulo State (Brazil) by the Soil Lifetime Index Methodology

Abstract

ABSTRACT:The soil is a key component of the Earth System, and is currently under high pressure, due to the increasing global demands for food, energy and fiber. Moreover, the management of agricultural systems is often inadequate and ignores the agricultural suitability of lands, and particularly the vulnerability of soils. This paper demonstrates the application of the concept of the Soil Lifetime Index (SLtI) for the entire state of São Paulo, at a spatial resolution of 30 m. The SLtI methodology represents a tolerance criterion and a diagnostic tool to assess the level of soil degradation by water erosion, based on estimated soil loss rates and on an average soil renewal rate. Two approaches were applied to determine: i) the remaining time (years) until the solum (horizons A + B) is removed by water erosion to a critical depth of 1.0 m (original approach); ii) the remaining time (years) until the top 0.25 m of the nutrient-rich soil surface is removed by water erosion (new approach). Several areas in the state have reached a very critical soil depletion level, due to the predominance of consolidated agricultural activities, mainly of sugarcane and livestock production (as in the mesoregions of Ribeirão Preto, Bauru, Assis, Itapetininga and Araraquara). Only 35 % of the study area is in conserved state; 65 % of the study area is in the state of resource degradation, requiring intervention to diminish soil loss rates -and of this total, SLtI is zero in 1 and 0.25 % of the study area, respectively, for the original (critical depth of 1 m) and the new approach (0.25 m). It was estimated that at the current soil loss rates, within 100 years, 20,000 km 2 of the total area of the state of São Paulo (248,209 km 2 ) will have reached the critical depth of 1.0 m, and the top 0.25 m of the soil surface from an area of approximately 76,000 km 2 will have been completely removed if the current pace of resource exploitation is maintained.

Combining regional to local restoration goals in the Brazilian Atlantic forest

“…One missing aspect in the ecological model is possibly the inclusion of an indicator of soil degradation/loss as a potential candidate to explain the low natural regeneration potential (or MBC) we estimated in our study. Soil degradation/loss reflects the land use history and inadequate agricultural practices (Medeiros et al 2016), which are very common in this region that have undergone different cycles of agricultural production since the nineteenth century (Silva et al 2017). Although other studies have also identified a low regeneration potential for the Paraiba Valley (Pandovezi et al 2018), we suggest that future studies could evaluate our estimated MBC by comparing it with field data.…”

Arable soil formation and erosion: a hillslope-based cosmogenic-nuclide study in the United Kingdom

“…To provide an insight into the sustainability of the soil profiles at RFF under arable agriculture, in terms of the balance of erosion and formation, a first-order lifespan model was employed. Calculating the sustainability of a net-eroding soil in firstorder terms has been attempted in the past (Elwell and Stocking, 1984;Sparovek and Schnug, 2001;Montgomery, 2007;Medeiros et al 2016). Early models (Stocking and Pain, 1983), however, did not account for mass inputs into the soil system, such as that derived from bedrock weathering.…”

Estimates of Annual Soil Loss Rates in the State of São Paulo, Brazil

“…The factor R is directly proportional to the product of two rainfall characteristics: total kinetic energy (Ec) and maximum rainfall intensity in 30 min (I30) (Bertoni and Lombardi Neto, 2012). In our study, however, we employed the annual erosion indexes determined by Medeiros (2016) (Figure 3), using the regionalized calculation method proposed by Mello et al (2013).…”

“…Therefore, the relationship between the estimated soil loss rate, soil renewal rate, and erosion tolerance can be a guideline in determining the stages of degradation. In other words, soil loss tolerance should be understood as a dynamic concept in space and time since it is defined in terms of soil loss and renewal rates, a methodological approach followed in another study (Medeiros et al, 2016). In practice, scientific studies on the dynamics of erosion in lands conditioned by spatial-temporal variation on a regional scale are limited by the limited availability of data.…”