Lessons from Ethiopian coffee landscapes for global conservation in a post-wild world

Abstract

The reality for conservation of biodiversity across our planet is that all ecosystems are modified by humans in some way or another. Thus, biodiversity conservation needs to be implemented in multifunctional landscapes. In this paper we use a fascinating coffee-dominated landscape in southwest Ethiopia as our lens to derive general lessons for biodiversity conservation in a post-wild world. Considering a hierarchy of scales from genes to multi-species interactions and social-ecological system contexts, we focus on (i) threats to the genetic diversity of crop wild relatives, (ii) the mechanisms behind trade-offs between biodiversity and agricultural yields, (iii) underexplored species interactions suppressing pest and disease levels, (iv) how the interactions of climate change and land-use change sometimes provide opportunities for restoration, and finally, (v) how to work closely with stakeholders to identify scenarios for sustainable development. The story on how the ecology and evolution of coffee within its indigenous distribution shape biodiversity conservation from genes to social-ecological systems can inspire us to view other landscapes with fresh eyes. The ubiquitous presence of human-nature interactions demands proactive, creative solutions to foster biodiversity conservation not only in remote protected areas but across entire landscapes inhabited by people.

Fig. 1. Challenges and opportunities in the conservation of genetic variation in crop wild relatives.

a A conceptual figure showing gene flow and introgression of genes from domesticated variants into the wild, across a mosaic landscape with different types of coffee populations in southwest Ethiopia. Both landraces and cultivars are considered domesticated variants of the crop, but in fact also the “wild” coffee is often managed and thus exposed to human selection. Wild coffee, landraces and cultivars often occur in a spatial mosaic as a result of both current and historical management. Dispersal of seeds and pollen causes gene flow (yellow arrows), but also infilling from more intensively managed coffee farms into the forests (white arrows) directly affect the genetic composition. Since these processes have been ongoing for some decades, the spatial configuration of genetic composition is likely more mixed than this simplified conceptual figure implies. Internal processes are explained in the next panel. b If possible, conserving large populations under more or less natural conditions along abiotic and biotic environmental gradients would allow spatially heterogeneous and balancing selection to operate in crop wild relatives and reduce threats from genetic swamping and introgression from domesticated variants. Such measures would maintain genetic diversity and resilience to future environmental changes. The grey arrow denotes different kinds of gene flow from domesticated variants into the natural habitats.

Fig. 2. Examining the trade-off between biodiversity and provisioning ecosystem services.

a In shade-coffee systems in southwest Ethiopia we identified three major management variables related to different types of intensification activities: Canopy cover (reflecting thinning of shade trees as well as a selection of trees with a canopy that is more permeable), Coffee Structure Index (capturing the active pruning of the coffee shrubs, but also correlated to the use of improved cultivars), and Weeding frequency (slashing of the ground vegetation, but also strongly correlated to other activities at the ground such as fertilization). a top and middle: When separately modelling the drivers of yield and tree species richness using the statistical approach ‘random forest’, we found that the same management action (high weeding frequency) explained both the lowest yields and the highest biodiversity. Yet, for the set of sites with higher yields and lower biodiversity, we found that variation in yield and biodiversity, respectively, were driven by different types of management: higher yields were attained by pruning (and associated practices), while higher biodiversity was associated with less canopy thinning. a Bottom: Trade-off curve between biodiversity and coffee yield (modified from). In the left part of the curve, we have the situation where the same management driver affects both the yield and the biodiversity, and in the right part of the curve, we have the situation where different drivers affect yields and biodiversity. b (i) In order to understand yield-biodiversity relationships it is important to separately study the effect of different management activities on yields and biodiversity. The figures show a conceptual framework describing how different components of management in an agroforestry system can affect both yields and biodiversity, as well as how external factors such as landscape connectivity and social-ecological contexts (affecting for example the cost of labour) interact to shape the relationships between yield and biodiversity. Biodiversity can also directly influence yields and thus modify the direct effects of management on yield.

Fig. 3. Beneficial and underexplored biodiversity in crop systems.

a Three examples of cryptic top-down control agents on coffee pests in southwest Ethiopian coffee systems. Top: The parasitism rate of the coffee blotch miner is higher in semi-forest coffee types than in more intensively managed plantations. Middle: A hyperparasite (white) supresses the growth of coffee leaf rust (orange) from the rainy to the dry season. Bottom: Herbivory is lower on coffee shrubs below shade trees with nests of Crematogaster ants. b Globally, there are many underexplored beneficial interactions: There are many studies on birds predating on herbivores and on pollination by bees, fewer on interactions with ants and mycorrhizal fungi, and very few on more cryptic interactions for example from parasitoids, hyperparasites, bats and beneficial microbes, let alone studies on multiple interactions or three-way interactions.

Fig. 4. Despite climate change posing a key threat to biodiversity in general, its indirect effects could in some instances also create restoration opportunities.

a In southwest Ethiopia, when the climate gets warmer farmers start to grow coffee at higher altitudes. This is likely to increase tree cover at higher altitudes, which had previously been cleared and currently is dominated by annual crop production. b In general, there are both direct and indirect effects of climate change on biodiversity. Indirect effects via land-use changes can pose severe risks to biodiversity, but need to be taken into account when planning adaptation policies to, if possible, search for new windows of restoration opportunities.

Fig. 5. Social-ecological systems perspective for conservation planning.

a In southwest Ethiopia spatial and temporal variation in rates of forest clearing can only be understood in the context of the interplay between population growth, top-down governance and how people value coffee both from a cultural and economic point of view. b In general, conservation planning needs to engage groups of stakeholders that together discuss how drivers and contextual variables affect conservation targets, in order to bring opportunities and challenges for more long-term and just conservation to the table.