Agricultural systems worldwide are undergoing changes due to shifts in a variety of factors including socioeconomic development, population growth and increasing variable and unpredictable climate conditions. Globally, the majority of farms are both small and family operated; 12% of the world’s agricultural land is operated by small farms, defined as occupying two hectares or less, and 75% is operated by family farms (Lowder et al. 2016). These small scale producers (SSP), also called smallholder farmers (SHF), are frequently mentioned as targets for development interventions, however, an operationalizable definition of a SSP or SHF is difficult to come by, with few sources even defining the term. A recent EPAR visualization of the sixteen categories of Sub-Saharan African Households attempts to provide a clear and consistent answer to the question: “Who is a smallholder farmer?”. SSP face multiple challenges as a result of a changing and increasingly variable climate, in part due to the highly heterogenous nature of SSP farming systems combined with their often limited adaptive capacity.

A recent EPAR research brief offers findings on observed or measured changes in precipitation, temperature or both on biophysical pathways and systems including land and soil, water, variable and changing growing seasons, and biotic stressors. The findings are the result of a review of relevant documents cited in Kilroy (2015), references in the IPCC draft Special Report on Food Security, and targeted searches from 2015 – present for South Asia and Sub-Saharan Africa.

What pathways did this research brief explore and why?

Impacts to Land and Soil

Impacts to land and soil include soil cover (including woody cover, tree cover, etc.), soil quality, soil moisture, soil nutrients (e.g. organic carbon), changes in species range, erosion, and desertification. Soil degradation results from changes in demographics as well as poor land management, which is further exacerbated by climate change (Niles et al. 2017).

Impacts to Water

Impacts to water include river and coastal flooding, glacial lake outburst flooding (GLOF), water table changes, salinization and changes to runoff, and streamflow. These impacts to water lead to negative agricultural impacts for farmers, particularly smallholder farmers, such as water logging and field conditions that are too wet for the use of heavy farm equipment (Ruane and Rosenzweig 2018).

Variable and Changing Seasons

Variable and changing growing seasons includes changes to temperature and/or precipitation in a specific season, longer or shorter growing seasons, shifts in the occurrence of a growing season, and shifts in the months with the highest or lowest rainfall. These changes have the potential to impact farmers in a way that is distinct from overall global, long-term climate signals (Ruane and McDermid 2017).

Biotic Stressors

Biotic stressors include pests, weeds, fungi, bacteria, algae and livestock disease. Climate change has the potential to impact the extent and timing of agricultural pests, resulting in negative outcomes for farmers.

What were our findings?

We found evidence of the impact of changes in temperature and precipitation (or both) on variable and changing growing seasons; extreme events; biotic stressors; crop yields; plant species density, richness and range; and streamflow; the number of studies associated with each biophysical pathway or system was summarized in a recent EPAR visualization. We found the most evidence related to variable and changing growing seasons; 22 studies reviewed describe increased variability or changes in growing seasons as a result of changes in temperature, precipitation, or both. Studies reflecting impacts due to or associated with increased temperature were found mostly on the Indian Subcontinent, though this strong evidence may have been due to the large number of documents sourced from Kilroy (2015), which focused on the climate change “hotspot” region glacial-fed river basins. Impacts associated with temperature were more widespread regionally. Strong evidence was also found related to the impact of climatic changes on the frequency and severity of extreme events in South Asia and Sub-Saharan Africa; 11 studies in total were found linking changes in extreme events to changes in temperature, precipitation, both temperature and precipitation, or unspecified climatic factors. Studies found an increase in the number and severity of extreme temperature events, as well as an increase in the number and severity of extreme rainfall events.

Less evidence was found related to the impact of changes in temperature and precipitation (or both) on the prevalence or dispersal of biotic stressors. We found four studies describing changes in the prevalence or dispersal of biotic stressors associated with observed or perceived increases in temperature, precipitation or both. Two additional studies report perceived changes to the prevalence of biotic stressors due to unspecified climatic changes. Moderate evidence was also found related to the impact of climatic changed on plant species density, richness and range in South Asia and Sub-Saharan Africa; five studies were found describing changes to species density, type, richness and range associated with changes in temperature or both temperature and precipitation.

Many reviewed studies related to farmer perception of climate change. Studies found farmers perceived changes related to seasonal temperatures, variability in growing seasons, the frequency and severity of extreme events, the prevalence and dispersal of pests and disease, and heat stress resulting in crop loss. These studies included surveys of farmers in Bangladesh, Madagascar, Nigeria and Pakistan, among other regions.

By Emma Weaver

Summarizing original EPAR research by C. Leigh Anderson, Alison Cullen, David Coomes, Elan Ebeling, Nina Forbes, Adam Hayes, Namrata Kolla, and Emma Weaver