More intensive or reduced coffee production on smallholder farms around Mount Kenya may threaten the conservation of valuable indigenous tree species, according to a new study.

In Kenya, smallholder coffee production has decreased by more than 50 per cent in the last 20 years due to lower market prices. Scientists are concerned that if farmers switch to growing annual food crops and fast-growing timber trees or intensify their coffee production, landscape diversity and tree species richness, composition and structure could be significantly affected.

Photo courtesy of Roast Works Coffee Company

A study published in the scientific journal Biodiversity Conservation found a relatively high level of tree species richness on 180 farms surveyed in Meru, Embu and Kirinyaga counties near Mount Kenya.

“We identified 190 different tree species in all, 78 per cent of which are indigenous,” says Sammy Carsan, Tree Domestication Scientist with the World Agroforestry Centre and lead author of the study. “This indicates that even with intensive management and changes in coffee production, small farms can make a valuable contribution to preserving important species.”

While the high level of diversity found on the coffee farms is not unusual for agroforestry systems, the actual number of indigenous trees is quite low.

“If coffee production in the area significantly decreases and farmers switch to crops such as maize and bananas, or they intensify coffee production with high yielding varieties, many indigenous trees are likely to be removed,” explains Carsan.

Supporting this, the study found that increasing yields of coffee (through intensification), banana and maize led to a decline in species richness and smaller tree structure on farms.

“If this is a trend that is likely to continue, it has the potential to impact on biodiversity conservation efforts by affecting the niches available for indigenous trees on farms,” says Carsan

Farmers around Mount Kenya tend to plant or retain remnant tree species along boundaries, contours and within their coffee plots. Among them, are several species of international conservation concern, including Vitex keniensis, Prunus africana, Premna maxima and Milicia excelsa.

In their research, Carsan and colleagues categorized the farms according to coffee production trends; i.e., whether yields had increased, decreased or remained stable over 5 years. Tree species richness (indigenous and exotic), abundance and composition were analyzed for 60 farms in each category.

The results suggest that farms with increasing coffee production have slightly higher species richness (including more indigenous species) and a greater number of trees. However these farms also tended to have lower tree densities and smaller trees.

On farms where production is stable, a greater number of small trees at higher densities were found. This suggests that these farmers may have increased tree planting activities while delaying a decision on whether to increase or reduce coffee production. Carsan believes these ‘indifferent’ farmers could play a significant role in maintaining or reducing farm niches for species of conservation value.

On farms with decreasing and stable production there was a greater abundance of introduced species, in particular Grevillea robusta and Eucalyptus species. This indicates that farmers are looking to supplement their coffee earnings with fast-growing timber trees.

Of particular concern is the overall low density of larger indigenous trees which could be attributed to increased tree felling for farm timber to meet high demand in the area. This has serious implications for regeneration, especially if more mother trees are removed. It could also lead to genetic erosion of some species as farmers tend to propagate materials from a limited number of mother trees either on their own or neighbors’ farms.

“Unless farmers can see the benefits of maintaining the range and quality of trees on their farms, long-term conservation benefits risk being lost,” suggests Carsan.

The trees which coffee farmers grow provide a range of useful products such as timber, fuelwood, fruits, medicines and fodder. They also provide important environmental services, including nutrient cycling, regulation of water fluxes, pollination and soil health.

“Protecting these trees relies on raising awareness among farmers about how indigenous species can provide timber for the sawn wood market and for domestic timber and firewood,” says Carsan. “People also need an understanding of the important role indigenous trees can play in household food security and income.”

The authors believe more research is needed to assess how farmers’ decisions about maintaining or reducing the number of mature indigenous trees on their farms can affect strategies to promote their conservation.

Download the study (with subscription):

Carsan S, Stroebel A, Dawson I, Kindt R, Swanepoel F, Jamnadass R. 2013. Implications of shifts in coffee production on tree species richness, composition and structure on small farms around Mt Kenya. Biodiversity Conservation 22 (12): 2919-2936.