Globally, coffee provides a livelihood for 125 million people. But forecasting models show that its cultivation has a poor future due to climate change. Sites suitable for growing Coffea arabica are predicted to decline dramatically. In that case, coffee producers would have to stop growing it or switch to growing Coffea canephora, known as robusta, which is less valued on international markets. Lenka Ehrenbergerová and her colleagues from the Institute of Botany, Dendrology and Geobiocenology at LDF MENDELU are researching to avert or slow down the darkest scenarios. The team has been conducting research on agroforestry coffee plantations across the American continent, as well as in Asia, for 15 years.
The first research took place in the Peruvian mountain forest in the Selva Central region. Measurements followed in Nicaragua, Cambodia, Costa Rica and Mexico. “In these areas, coffee is grown in agroforestry systems, i.e. together with trees, so the main aim of the research is to find out how tree cover affects coffee trees, whether it is a suitable tool for combating climate change and whether growers could get involved in carbon trading,” explained Lenka Ehrenbergerová.
Specifically, the research in Peru had multiple levels. One focused on the aforementioned carbon fixation in different types of agroforestry systems with coffee. Thanks to the work of the Brno experts, local growers gained a better understanding of how to enter carbon fixation programmes. Another level of research focused on the effect of the screen on the incidence of coffee rust, a disease that has largely decimated coffee plantations and in some years has resulted in high coffee price increases on world markets. “Higher rates of coffee rust in shaded agroforestry plantations are often the reason why growers cut down trees on their plantations and switch to monoculture cultivation. However, this trend was not confirmed in our study. The density of the coffee trees played a much bigger role, as did their higher age,” explains the researcher.
Experts have advised growers to reduce the density of plantations and to renew coffee plantations earlier. They also wanted to encourage growers to plant trees on coffee plantations, as the sale of wood from agroforestry plantations can be an additional source of income for growers. For this reason, they also focused on identifying the wood stocks of the trees under cultivation. “The main shade tree species in the area were the local species of the genus Inga, from which hardly any timber is used, as well as introduced species of the genus Eucalyptus and Pinus. Unfortunately, these species are not suitable for coffee agroforestry systems due to their high water requirements in the case of Eucalyptus and dense shade in the case of Pinus. On the other hand, their growth rates are very good, reaching the clearing age after only 15 to 20 years,” said Ehrenbergerová.
Scientists have found that native species also serve well as shade trees and have seen better growth rates than introduced species. This is the case, for example, with the native tree Retrophyllum rospigliosii, an evergreen conifer native to the montane rainforests of South America, which is only found on the edges of plantations. Growers have been advised to focus more on this species.
Research on coffee plantations in other countries in Asia and South America was summarised by Lenka Ehrenbergerová on behalf of the Institute of Botany, Dendrology and Geobiocenology: “In Cambodia, we focused our research on monitoring the effect of shade on the size of coffee beans. There was no difference in coffee bean size in the context of robusta coffee trees grown with and without a screen. In Nicaragua, we conducted carbon fixation measurements in coffee plantations and a questionnaire survey with growers. The measurements have been extended to Costa Rica and are now in the data evaluation phase. A completely new research on coffee plantations in Mexico was started this year by PhD student Karolína Chalupová. With this research we will test some of our other hypotheses.”
In the future, the researchers also want to install new plots in Ethiopia, where the institute has long been active. Discussions are currently underway with several universities, mostly in Latin America, to develop uniform methodologies for measuring coffee plantations.
In addition to scientists, the research on coffee trees also involves bachelor and master students from the Faculty of Forestry and Wood Technology and the Faculty of AgriSciences at MENDELU, who have already produced several theses on the subject.
Agroforestry
The cultivation of agricultural crops under trees is known as agroforestry and is a cultivation method that increases biodiversity, protects the soil against erosion, diversifies the growers’ production and, in the case of coffee trees, helps to create a better microclimate for the plants.