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Abstract:
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"Plant invasions, affecting ecosystem recovery and household economics, are an important part of land-use change in the Calakmul region, Mexico, closely related to ecosystem function and homogenization of landscapes. Bracken fern has increased four-fold in the area since 1985, impeding regular succession of the vegetation and affecting the amount of areas under forest opened for cultivation. The general assumption drawn from the literature links this invasion to land degradation, but the spatial distribution of bracken fern and its relation with land-use suggests a more complex process involving land-use strategies, land degradation, and fire regimes.
"The distribution of bracken fern in the region is characterized by low density of bracken in landsparse areas where intensive cultivation is predominant (swidden cultivation coupled with commercial chili production), and a high density in land-surplus areas characterized by less intensive cultivation (former large-scale agricultural and cattle projects). For the most part, cooperative projects clearing large amounts of continuous terrain have taken place in the older and larger ejidos in which households have up to 100 ha in usufruct land. In such land surplus conditions, there is little incentive to combat bracken fern on non- household land or to invest the scale of labor needed on household lands, given other, viable options. Alternatively, where land is scarce and the household economy dependent largely on cultivation, the fern is attacked through labor.
"These circumstances and responses are consistent with small- holder behavior among hybrid (subsistence and market) producers. Bracken fern can be seen as a perturbation, similar to drought, to which farmers must decide if and how to allocate their labor and capital. The apparent rewards to combating bracken fern, given its high labor costs, are low compared to offfarm and NGO- and state-sponsored and state-subsidized activities. Where the latter are a significant option and land pressures are low, the investment is not made. In contrast, where commercial chili cultivation is important and land pressures are high, the investment is made. The labor invested does not intensify cultivation as much as it helps to alleviate a perturbation on production or loss of land."
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