Functional traits represent a key nexus between scientific and local knowledge

Continuing our Special Feature series, Functional traits in agroecology, Marney Isaac comments on her paper, Farmer perception and utilization of leaf functional traits in managing agroecosystems.

Using leaf functional traits to understand plant response to environmental change is well-established for research in a wide number of natural ecosystems, and now being more widely applied to agroecosystems. Yet, little is known about if, or how, farm managers actually use information on leaf functional traits to inform management decisions. We do know that farmers evaluate the impacts of management based on observable and tactile characteristics of crops, some of which are directly in line with leaf functional traits, such as leaf colour, size, and thickness. And sociological research further suggests that the degree to which farmers make decisions based on plant characteristics that are not strictly related to yield is contingent on the type of management practices one employs. For instance, there is reason to expect farmers who manage for greater on-farm diversity are likely to use a more detailed understanding of functional traits in decision-making.

Using shade-grown coffee systems in Costa Rica as a case study, we recorded how coffee farmers ranked coffee leaves in terms of key functional traits (including leaf size, leaf thickness, and leaf color) in comparison to defined environmental scenarios. We were trying to get at whether or not farmers associate certain leaf traits with particular management conditions, including shaded to high light environments and low soil fertility to sufficient soil nutrition conditions. In this way, our research could 1) assess whether farmers observe and use leaf trait variation as indicators of management conditions. From there, we were then interested in 2) testing whether farmer observations of leaf trait responses to environmental conditions match up with the trait-environment relationships that ecological research has observed. Lastly, we were 3) interested in identifying the farmer- and farm attributes that best predict whether or not farmer understandings of local trait-environment relationships are the same as those observed in scientific papers.

Employing our “leaf book” as a visual elicitation tool – literally, a number of leaves with different physical appearances mounted in a book – we demonstrate that farmers use crop leaf variation as means to 1) evaluate the environmental conditions on their farms, and 2) start to devise and initiate management actions including shade-tree species selection and abundance, crop- and shade-tree pruning regimes, and fertilisation treatments.

The majority of farmers demonstrated a complex and highly nuanced system of utilising coffee traits as indicators of management practices. Farmers managing smaller farms tended to more commonly observe and use coffee leaf traits in decision making, as compared to those managing large farms. Interestingly, farmers who identify changes in leaf thickness in response to environmental conditions, also report physically inspecting their coffee leaves: a farmer who touches their coffee leaves has a much more distinct sense of what leaf thickness variability tells us about management.

Our findings signify that functional traits represent a key nexus between scientific and local knowledge. Despite a large and growing number of independent analyses on i) trait variation in the ecological literature, and ii) local knowledge of crop traits for agricultural management and decision-making, there are still few studies to date that have integrated these two fields. Linking both natural and social science theory and methods, our research provides solid evidence to indicate that plant functional traits could act as a basis to evaluate and devise management prescriptions, for both farmers and researchers working in biologically complex agroecosystems.

It is very exciting to see multiple papers in this issue of Journal of Applied Ecology that focus on the relationship between local and scientific knowledge. These papers are two examples that acknowledge the critical role that local knowledge plays in the field of ecology, and contribute novel advances to decades of research on local ecological knowledge. Yet, as our paper explicitly suggests, within this field caution must be made to not exclusively focus on “testing the accuracy” of local knowledge. These two bodies of knowledge vary both spatially and temporally. Impressing a verification angle to locally derived understandings of environments creates power dynamics that undoubtedly must be kept in mind. As our research shows, it would serve contemporary applied ecology well to accept and embrace a pluralistic approach to environmental knowledge.

The full article, Farmer perception and utilization of leaf functional traits in managing agroecosystems is a part of the Special Feature, Functional traits in agroecology and available in Journal of Applied Ecology.

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