Agricultural Intensification Exacerbates Spillover Effects on Soil Biogeochemistry in Adjacent Forest Remnants

Abstract

Land-use intensification is a central element in proposed strategies to address global food security. One rationale for accepting the negative consequences of land-use intensification for farmland biodiversity is that it could ‘spare’ further expansion of agriculture into remaining natural habitats. However, in many regions of the world the only natural habitats that can be spared are fragments within landscapes dominated by agriculture. Therefore, land-sparing arguments hinge on land-use intensification having low spillover effects into adjacent protected areas, otherwise net conservation gains will diminish with increasing intensification. We test, for the first time, whether the degree of spillover from farmland into adjacent natural habitats scales in magnitude with increasing land-use intensity. We identified a continuous land-use intensity gradient across pastoral farming systems in New Zealand (based on 13 components of farmer input and soil biogeochemistry variables), and measured cumulative off-site spillover effects of fertilisers and livestock on soil biogeochemistry in 21 adjacent forest remnants. Ten of 11 measured soil properties differed significantly between remnants and intact-forest reference sites, for both fenced and unfenced remnants, at both edge and interior. For seven variables, the magnitude of effects scaled significantly with magnitude of surrounding land-use intensity, through complex interactions with fencing and edge effects. In particular, total C, total N, δ15N, total P and heavy-metal contaminants of phosphate fertilizers (Cd and U) increased significantly within remnants in response to increasing land-use intensity, and these effects were exacerbated in unfenced relative to fenced remnants. This suggests movement of livestock into surrounding natural habitats is a significant component of agricultural spillover, but pervasive changes in soil biogeochemistry still occur through nutrient spillover channels alone, even in fenced remnants set aside for conservation. These results have important implications for the viability of land-sparing as a strategy for balancing landscape-level conservation and production goals in agricultural landscapes.

Eutrofização de solos e comunidade arbórea em fragmentos de uma paisagem agrícola

“…Trabalhos recentes concluem que, independentemente do tamanho dos fragmentos, as áreas de borda são mais vulneráveis ao uso do solo adjacente a elas e apresentam alterações de grande importância na fertilidade do solo (Duncan et al, 2008;Chabrerie et al, 2012;Didham et al 2015). Dessa forma, a adoção de barreiras físicas (Didham et al, 2015) e de práticas agrícolas que permitam o menor movimento do solo, a exemplo do plantio direto, pode ser importante ferramenta na conservação da biodiversidade em paisagens agrícolas.…”

“…Cada uma das variáveis foi comparada de forma pareada entre os sítios de mesma escala de tamanho. Os métodos aqui utilizados têm sido exercitados em trabalhos recentes (Duncan et al, 2008;Chabrerie et al, 2012;Didham et al, 2015), atendendo com acurácia à análise dos dados obtidos.…”

“…O sistema chamado de poupa-terra, do inglês "land sparing", considera que o aumento da produtividade reduziria a pressão da agricultura sobre os remanescentes de áreas naturais, uma vez que minimizaria a conversão dos ecossistemas naturais em áreas produtivas (Tscharntke et al, 2012). Entretanto, Didham et al (2015) alertam que ignorar o reflexo do manejo adotado nos diferentes usos do solo sobre a escala da paisagem é um dos equívocos ocasionados por abordagens compartimentalizadas.…”

1. Forests, Trees and Landscapes for Food Security and Nutrition

“…Links between the intensification of agricultural systems (through increased fertiliser application, pesticide use, animal stocking rates and irrigation) and in situ declines of biodiversity on farmland have been well documented Kleijn et al, 2009), even though biodiversity loss need not necessarily accompany increased agricultural yields across all systems . Meanwhile, the potential ecological impacts of "spillover" effects (Matson and Vitousek, 2006;Didham et al, 2015), from the agricultural matrix into adjacent natural systems (e.g. inputs of nutrient subsidies through fertiliser drift and down-slope leaching (Duncan et al, 2008), livestock access (Didham et al, 2009) and the spillover of predator or consumer organisms (Blitzer et al, 2012)) could likely compromise the effectiveness of land sparing strategies.…”

Magnesium capability to attenuate the toxicity of aluminum on the growth of Saccharomyces cerevisiae PE-2

“…Aluminum toxicity is especially raised when soil acidity is intensified by land-use intensification, i.e., industrial activities, and fertilization with acid action fertilizers (DIDHAM et al, 2015;FAGERIA;NASCENTE, 2014). Tropical South America has an amount of 85% of acid soils, of which about 24% in located in the central part of Brazil (FAGERIA;NASCENTE, 2014).…”