Agriculture in flux, biodiversity in the balance: conservation implications of cropland expansion and abandonment

Abstract

Agriculture has transformed our planet, nourishing humans but also driving habitat loss and subsequently threatening biodiversity, emitting carbon, and eroding ecosystem services. Yet agriculture is currently in a state of flux: expanding in many places to meet rising food demands but contracting elsewhere as broad socioeconomic, demographic, and technological changes cause people to leave rural areas. As expansion and abandonment rearrange our world, reconciling agricultural needs with the maintenance of biodiversity remains a defining challenge for conservation. In this dissertation, I combine geospatial modelling with field data to contribute to three dimensions of this challenge: using land-use prioritization to minimize the impact of expansion (Chapter 1), understanding the conservation potential and limitations of the increasing trend of abandonment (Chapter 2 and 3), and exploring ways to reduce the impacts of agricultural practices in situ (Chapter 4). In my first chapter, I use a land-use prioritization model designed to guide agricultural expansion in Zambia to show that different methods for measuring biodiversity produce radically different recommendations as to which regions to protect for biodiversity or convert to agriculture. I suggest ways to improve how biodiversity is incorporated into land-use decisions. In Chapter 2, I use high-resolution land cover maps to explore how agricultural abandonment affects biodiversity and carbon stocks.I present a quantitative assessment of the persistence of abandoned croplands, revealing that abandonment is often ephemeral, seriously limiting the benefits associated with regeneration of abandoned farmland. In Chapter 3, I combine abandonment maps with biodiversity data to show that abandonment results in habitat gains for most bird and mammal species, but rarely compensates for habitat loss due to other factors. These studies demonstrate substantial potential but significant current constraints on the ability for abandonment to contribute to biodiversity and carbon goals. Finally, Chapter 4 investigates ways to enhance the sustainability of livestock grazing in Kenya’s savanna ecosystems, linking high-level conservation planning to the local-scale interventions that underpin most conservation practice. Together these chapters highlight the importance of pursuing conservation simultaneously across these three dimensions of agricultural land-use change to safeguard biodiversity for future generations.