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.

Figure 1. Land use change image 1984–2000 for the Kiambu area (Kenya) (background scene: Brightness image 1984).

Figure 2. Land use change image 1984–2010 for the Kiambu area (Kenya) (background scene: Brightness image 1984).

Figure 3. Mean number of berries per branch in a shaded and a sun-grown coffee plantation in Kiambu (Kenya) during the period June 2009 to June 2011.

Figure 4. Mean Hypothenemus hampei infestation level in shaded and sun-grown coffee plantations in the Kiambu area (Kenya) during the period June 2009 to June 2011.

Figure 5. Effect of mean, maximum and minimum monthly temperature on Hypothenemus hampei infestation level under shaded and sun-grown coffee plantations in Kiambu (Kenya) between June 2009 and June 2011.

Figure 6. Effect of rainfall (mm) on Hypothenemus hampei infestation level under shaded and sun-grown coffee plantations in Kiambu (Kenya) between June 2009 and June 2011.