Melting Pots of Biodiversity: Native and Introduced Plants in Tropical Smallholder Farming Landscapes

By Christian Kull, Associate Professor at Monash University, Australia

For the past week the Landscapes Blog has taken a closer look at trees and forests in the context of agricultural landscapes. While there is often an emphasis on native vegetation in conserving or restoring landscapes, introduced species of plants play a significant role in shaping the structure and character of the landscape. Today, guest author Dr. Christian Kull explains the contributions of non-native plant species to the livelihoods, culture, and sustainability of communities within these mosaic landscapes.
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What happens when, in a particular tropical landscape, you combine human labor, introduced plants, and diverse societal histories and structures? You end up with anthropogenic or cultural landscapes – the “matrix” in current ecological jargon – such as the domesticated forests of Southeast Asia, the tree gardens of Caribbean or Pacific islands, the shambas of Africa, the rice terraces of Madagascar. Despite their aesthetic and cultural attractions, these smallholder farming landscapes are directly or implicitly critiqued by many – for not being as productive as modern industrial agriculture, for trapping people in rural poverty, and for taking up space at the expense of natural habitats.

In an article in the current issue of Environment magazine, we use the lens of introduced plants to engage this debate. One aspect of the critique of smallholder farming landscapes is the concerns of biodiversity conservation: these landscapes can be seen as competing with ‘wild’ nature for land, they contain only a diluted set of native biodiversity, and they serve as conduits for threatening invasive species. Smallholders have, of course, a long history of incorporating new plants from around the world into their farming activities. The field of invasion biology would typically urge caution about the negative impacts of non-native species. Yet invasion biology is currently rife with debate over whether to judge plants on their alien status or on their impacts, and how to deal with radically transformed environments (most visible, perhaps, are the positions of Mark Davis and Dan Simberloff in the pages of Nature; see also the dispute between Tim Low and us in Biological Invasions).

In the Environment article, we argue that the arrival of non-native plants in these ever-changing landscapes must be seen more holistically. While a small subset of both native and introduced plants can display noxious behavior, the majority can contribute to people’s adaptation to social and environmental changes, to a diversification of livelihoods and habitats, to avoided deforestation, to biodiversity conservation, and finally to sustainability.

The article proposes a simple analytical framework to judge the value of smallholder farm landscapes mixing native and alien species. This framework centers on three criteria:

1. Productivity: are these landscapes sustainable and resilient sources of products useful to subsistence and economic activities, locally and beyond?
2. Community: do they contribute to the vibrancy, social justice, and resilience of culturally rich rural communities?
3. Environment: are they resilient contributors of ecosystem services, aiding or at least not damaging biodiversity conservation, water resources, and soil fertility?

These criteria are applied to case studies describing the rubber gardeners of Indonesia, the cacao farmers of Cameroon, and the rice and eucalyptus smallholders of Madagascar.

We suggest that certain smallholding tropical farm landscapes be called “melting pots”, for they mix native and alien species and are jointly built by farmers and by natural processes. They blur boundaries between human and natural, native and non-native, production and conservation. We chose this term in direct reference to the hotspot approach to conservation, which was not built to cope with a world dominated by anthropogenic spaces where people introduce species and build a different kind of biodiversity. The melting pot concept promotes a focus on hybrid biological and social processes, on the novel ecosystems that can result, rather than emphasizing distinctions between people and nature.

Hot spots and melting pots are complementary, but not enough recognition, attention, and promotion go to the latter. Focusing conservation and development efforts on encouraging and protecting melting pot landscapes is, for us, the missing link in the paradigms of conservation and sustainable development. Melting pot landscapes can be sustainable sources of useful products, can facilitate vibrant and resilient rural communities, and can be resilient contributors to the functioning of local and global biophysical systems.

Read more:
Kull, C.A., S.M. Carriere, S. Moreau, H. Rakoto Ramiarantsoa, C. Blanc-Pamard, and J. Tassin. 2013. Melting pots of biodiversity: tropical smallholder farm landscapes as guarantors of sustainability. Environment 55(2): 6-16.