Harvest of non-timber forest products (NTFPs) has been promoted as an opportunity to both enhance local livelihoods and contribute to biodiversity conservation (Leisher et al. 2010). At the same time, the effectiveness of NTFP harvest at achieving these goals has been criticized (Belcher and Schreckenberg 2007), and over-harvest is considered a major threat to plant diversity (Brummit and Bachman 2010). This contrast between goals and outcomes illustrates the need to improve our understanding of the circumstances in which NTFP harvest can make a meaningful contribution to local livelihoods without having negative environmental consequences.
Widespread and abundant non-timber forest product (NTFP) species have a high potential to be harvested sustainably (Cunningham 2001). Because of their high levels of biomass, however, these same species are likely to influence ecosystem processes and have significant interactions with other components of the ecological community, interactions which may be altered by harvest (Gaston and Fuller 2008; Gaston 2010). If promoting NTFP harvest is meant to contribute both to local livelihoods and to the conservation of ecosystems, it is critical to assess the sustainability of harvest from an ecosystem perspective, especially for common species.
Many heavily harvested NTFP species are locally abundant and/or widely distributed. For example, several species of shrubs, grasses, and reeds that are harvested to make hand brooms in South Africa are locally dominant, respond positively to disturbances such as grazing or fire, or are otherwise considered “weedy” (Shackleton 2005). Similarly, the multi-use palm Phoenix reclinata Jacq. is widely distributed across temperate and tropical Africa (Barrow 1998) and can be one of the most abundant species where it occurs (Kinnaird 1992). Studies of the ecological impacts of harvest of these kinds of common species are limited compared to studies that focus on species perceived to be rare or in decline, often under the expectation that abundant and disturbance-tolerant species have a high potential for sustainable harvest (Reid 2005; Shackleton 2005; Shackleton et al. 2009).
While there may be a high potential for sustainable harvest of common species from a population-level perspective, high levels of harvest are particularly likely to alter ecological interactions and ecosystem processes. A plant species’ abundance is an important determinant of its influence on ecosystem structure and function, with more abundant species generally having a greater effect than rare species (Grime 1998). An emphasis in the NTFP literature on studying the population dynamics of rare and declining species could lead to the biased conclusion that ecological interactions and ecosystem-level effects resulting from harvest are generally unimportant. This difference in the ecological role of abundant species means that while high levels of fruit or seed harvest can have negligible impacts on populations of common, long-lived, clonally reproducing plant species (Ticktin 2004), harvest may still negatively affect frugivores, including birds (Moegenburg and Levey 2003) and primates (Kinnaird 1992) that rely on that fruit for food. When harvest involves removing large amounts of biomass from an ecosystem, this may also alter nutrient cycles (O’Hara 1999).
Despite growing recognition that NTFP harvest affects and is affected by management practices and ecological interactions at multiple levels, these interactions are rarely studied above the population level (Ticktin 2004). Understanding the larger ecological context in which harvest of common NTFP species occurs is necessary to devise appropriate management plans to maintain both the economic and ecological roles of such species. If harvest occurs without an awareness of the many ecological interactions that it can affect and be affected by, the cascading effects of harvest could have large, unanticipated consequences both for ecological processes and the people who rely on them (Estes et al. 2011).
We use a case study of mountain date palm (Phoenix loureiroi Kunth, formerly P. humilis) to present a conceptual framework for considering the broad ecological consequences of harvesting common NTFP species. Mountain date palm is a widespread and common species, heavily harvested for its leaves in India’s southern Western Ghats. Information about the ecology, current harvesting intensities, and management practices of mountain date palm is not available. We integrate data on the extent and levels of commercial harvest, local management practices, the ecological context in which harvest occurs, and research on harvest effects to (1) document the intensity and extent of mountain date palm harvest in the southern Western Ghats, (2) identify the ecological implications of harvest, and (3) demonstrate how a framework that considers harvest in the context of ecological communities and ecosystems is important for assessing the impacts of harvest of common NTFP species.