A New, Social Science-based Approach to Improve Weed Management

A corn field in Colombia that has been overgrown by a morning-glory-type weed.
A corn field in Colombia that has been overgrown by a morning-glory-type weed.

In the early days of New England, many towns and villages set aside a fenced field, the common, where residents could safely pasture their sheep, cows or other livestock for the day. But the arrangement came with a dilemma that became known as “the tragedy of the commons” – it turned out to be unsustainable. Individuals acting in their own self-interest eventually threatened the resource by over-use, depleting and spoiling it for everyone.

This concept is at the heart of a new approach to the global problem of weeds – whether ecological or agricultural invaders – recently advocated by an unusual international collaboration of plant scientists and social scientists that included evolutionary biologist Ana Caicedo, biology. In their recent publication in “Nature Plants,” they propose that a new, nuanced approach can be helpful in protecting shared-resource plant systems around the world.

The authors point out, “One major reason for the failure to effectively manage weeds at landscape scales is that current Best Management Practice guidelines, and research on how to improve such guidelines, focus too narrowly on property-level management decisions.”

As Caicedo recalls, the group that formed after a workshop on weeds and invasive species held in Canada in 2016. It brought ecologists, agronomists, weedscientists, foresters, evolutionary biologists and a wide range of social scientists together to address the topic.

Caicedo, an expert in the evolution of weedy rice, recalls, “We were quite a mix, and especially the social science was really new to me. None of us was an expert in this approach, we all had to learn from the others. This paper was born out of that trans-disciplinary workshop on how can we solve some of the problems that weedy plants cause all over the world. This not what I usually do, I’m a plant geneticist, but it was exciting and very interesting.”

One thing Caicedo learned, she says, is that the tragedy of the commons has a rich body of social science research surrounding it, including tools for identifying and examining resources as either a “public good” or as a “common pool resource” (CPR). These differ in the nature of the trade-offs between individual and collective interests. Each has management practices and techniques – known as design principles – that can be put in place to help ensure that individuals cooperate and don’t use the resource up. 

For this work, Caicedo and colleagues and identified four common problems – achieving plant biosecurity, preventingweed seed contamination, maintaining weed herbicide susceptibility and sustainably using biological control– that weedy plants cause, and whether they fall into the public good or CPR category. For each problem, they then asked whether examples of successful management of the resources existed, and which design principles were the ones implemented successfully.

Caicedo says, “We found that when you work on solving a problem caused by weeds, individual action is not going to work; it really must be collective action. That realization led us to recommend a regional or landscape-level approach for all of the examined scenarios.”

Evaluating the public good or CPR characteristics of each specific weed management problem can lead to the application of the design principles most likely to encourage cross-boundary cooperation. She adds, “Each type of weedy problem has its idiosyncracies, but there is a way to approach each of them.”

The authors, led by Muthukumar Bagavathiannan of Texas A&M University and social scientist Sonia Graham of the University of New South Wales, hope their conclusions and recommendations will be useful to government, agronomists, social scientists, extension agents, ecologists and resource managers, for example.

Caicedo adds, “We hope to have provided a new tool, or at least a new way to think about this wicked dilemma. It’s a wake-up call that we have to start thinking of weed management not in a ‘whack-a-mole’ way, but more as a collective effort.”

The authors conclude, “We believe that the approach presented here applies to a majority of landscape-scale weed management issues beyond the four case studies described, yet acknowledge that case-specific analyses are imperative for confirming the existence of social dilemmas, application of specific design principles and determining suitable strategies for successful weed management.”

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