Climate Change or Urbanization? Impacts on a Traditional Coffee Production System in East Africa over the Last 80 Years

Abstract

Global environmental changes (GEC) such as climate change (CC) and climate variability have serious impacts in the tropics, particularly in Africa. These are compounded by changes in land use/land cover, which in turn are driven mainly by economic and population growth, and urbanization. These factors create a feedback loop, which affects ecosystems and particularly ecosystem services, for example plant-insect interactions, and by consequence agricultural productivity. We studied effects of GEC at a local level, using a traditional coffee production area in greater Nairobi, Kenya. We chose coffee, the most valuable agricultural commodity worldwide, as it generates income for 100 million people, mainly in the developing world. Using the coffee berry borer, the most serious biotic threat to global coffee production, we show how environmental changes and different production systems (shaded and sun-grown coffee) can affect the crop. We combined detailed entomological assessments with historic climate records (from 1929–2011), and spatial and demographic data, to assess GEC's impact on coffee at a local scale. Additionally, we tested the utility of an adaptation strategy that is simple and easy to implement. Our results show that while interactions between CC and migration/urbanization, with its resultant landscape modifications, create a feedback loop whereby agroecosystems such as coffee are adversely affected, bio-diverse shaded coffee proved far more resilient and productive than coffee grown in monoculture, and was significantly less harmed by its insect pest. Thus, a relatively simple strategy such as shading coffee can tremendously improve resilience of agro-ecosystems, providing small-scale farmers in Africa with an easily implemented tool to safeguard their livelihoods in a changing climate.

Contrasting effects of shade level and altitude on two important coffee pests

“…Our work supports recent papers suggesting that provision of shade trees is likely to be an effective way of managing coffee berry borers (Teodoro et al 2008;Jaramillo et al 2009Jaramillo et al , 2011Jaramillo et al 2013;Karp et al 2013), but contradicts studies that either failed to show an effect of shade (Soto-Pinto et al 2002), or indicated that excessive shade may increase borer problems (Willey 1975). Together, this suggests that shade tree provision is an effective approach to manage coffee berry borers in many situations but that this may not be the case at all locations or shade levels.…”

“…It has been shown that biological control of the coffee berry borer is more effective in forested coffee plantations (Karp et al 2013;Railsback and Johnson 2013), and that abandoned coffee plantations may have lower coffee berry borer abundances compared to managed coffee agroforests with lower levels of shade (Teodoro et al 2008). Recently, Jaramillo et al (2013) found higher coffee berry borer infestations in a sunexposed coffee plantation compared to a shaded one. Other studies, however, failed to show an influence of shade on coffee berry borers (Soto-Pinto et al 2002), and some older observations even indicate that excessive shade may increase coffee berry borer attack rates (Willey 1975).…”

Impact of climate change on the agro-ecological innovation of coffee agroforestry systems in Central Kenya

“…Annual production and share of coffee in the County's GDP have significantly declined. Climate change is one of the major factors affecting coffee production: it induces the coffee trees to dry, increases the incidence of coffee pests and diseases (Jaramillo et al 2013), depresses tree growth and provokes coffee flower abortion (Thuku 2013). Future projections (Laderach et al 2011) indicate the optimum coffee-producing zone will shift still higher to the 1680-1800 masl range to compensate for expected temperature increase in the lower altitude ranges (Craparo et al 2015;Laderach 2011).…”

“…However, rainfall reduces from time to time while hot periods become more common. As a result, coffee plants tend to dry, while pests and diseases develop, affecting many coffee growers (Jaramillo et al, 2013).…”

“…This has two reasons. First, warmer temperatures and erratic rainfall (Asayehegn et al 2017) induced the transformation of potential areas to semi-arid zones, where a unit minimum temperature increase is subjected to a yield decline of 137 kg per hectare (Craparo et al, 2015), and second, the climate change derived infestation of Coffee Leaf Rust (CLR) and Coffee Berry Diseases (CBD) caused transformation of previously potential coffee areas to marginal coffee or food crops (Jaramillo et al, 2014).…”