Ecological and social outcomes of urbanization on regional farming systems: a global synthesis

Abstract

Though urban land covers only around 0.5% of the Earth’s terrestrial surface, urbanization often leads to significant changes in land use and land cover. However, knowledge on the ecological and social outcomes of urbanization is largely fragmented across a multitude of local-level studies. We synthesized the outcomes of urbanization on 15 ecological and social variables associated with regional farming systems, namely water quality, agro-biodiversity, carbon sequestration, control of invasive species, soil fertility, control of soil erosion, pollination, cultural identity, food security, income and employment, demographic stability, conflict mitigation, social network, health and education, and equity. From 246 cases, positive, negative, and non-conclusive urbanization outcomes were extracted. Additionally, distributions of these outcomes by continent, population size of towns/cities, national per-capita GDP, and dominant farming systems were assessed. As a result, more negative than positive outcomes were found. Although ecological outcomes were largely negative, social ones were mostly positive. Threats to water quality, demographic stability, and cultural identity arose as particularly pressing issues. The ecological outcomes related to pollination were largely positive but all other ecological variables reported higher negative outcomes. The social outcomes related to the economic viability of farming and employment were largely positive, whereas those related to cultural and equity aspects were predominantly negative. The ecological outcomes were frequently negative in the Global South, medium-large cities, poor countries, and for livestock or fishery systems. The social outcomes were more frequently negative in the Americas, highly populated cities and megacities, wealthy countries, and for livestock and fishery systems. The threats and opportunities of rural–urban transformations in different dimensions and contexts of farming systems should be considered in any urban planning strategy.