This post is also available in Tumbuka here.
Cassandra Vogel and Vera Mayer present their latest research into the effects of habitat loss on butterflies in Malawi, suggesting that encouraging smallholders to increase the diversity of flowering crops and implement sustainable soil practices is needed.
Habitat loss and butterflies
The African Miombo woodland ecoregion spanning form Angola to Mozambique is a unique habitat for many endemic plant and animal species. Unfortunately, this highly biodiverse area is at risk of decline. One of the major drivers of this threat is the conversion of woodland to farmland. Most farmers in this part of the world are smallholders, managing less than 2 hectares of land on which they depend for food security and livelihoods.
By now, it is well-known that habitat loss as well as the intensification of farm management (for example through the use of synthetic inputs or by growing crops in monoculture) has negative effects on insect biodiversity. This can endanger ecosystem services, such as pollination, that insects provide to both farmers and natural ecosystems. Unfortunately, almost all of our knowledge of these effects come from large-scale agriculture in temperate areas.
In comparison, there is little known about the effects of habitat loss on insects in the tropics, especially in sub-Saharan Africa. So, what can be done to mitigate the negative effects on insect communities, once habitat is converted to farmland? Involving smallholders could be key through their implementation of sustainable farming known as agroecology.
Agroecology aims to decrease dependency on synthetic inputs, for example, by intercropping or mulching to maintain soil health, or managing pests using botanical extracts and encouraging natural enemies. In particular, diversifying agroecological practices has benefits for smallholder farmers, such as improving food security, but so far it is not known if implementing a diversity of agroecological soil or pest management practices has co-benefits for insects.
Why study butterflies in Malawi?
To fill these knowledge gaps, we studied butterfly communities in 24 paired woodland and farmland sites in Malawi, located in landscapes varying in surrounding woodland cover. Malawi, situated in the Miombo woodland ecoregion, faces many common challenges such as rapid deforestation.
However, smallholder communities in northern Malawi are also enthusiastic adopters of agroecological practices, which are promoted by our partner NGO: Soils, Food and Healthy Communities. Our project aimed to support interdisciplinary collaboration by actively involving the smallholder farmers in the research. This gave us the opportunity to compare woodland to farmland habitats and to study the effect of different woodland cover in the surrounding landscape on local smallholder farms. On farmland sites, we additionally studied the effects of the number of agroecological soil and pest management practices and the richness of flowers on butterflies.
We decided to study butterflies since they are good indicators for environmental changes due to their variety of traits. In addition, on a more practical level, the butterfly species of southern Africa are quite well-known and described (especially compared to other insect groups), meaning that we could identify the observed butterflies to species level, and gather information on their traits.
What did we find?
We found farmlands had almost half the abundance and richness of butterflies compared to woodland. Overall, butterfly abundance was not affected by landscape-scale woodland cover, but the species richness increased in both habitats with increasing woodland cover.
Interestingly, we found that butterfly abundances were mostly driven by a single hyperabundant species: Catopsilia florella. Butterfly species with certain traits, such as a small wingspan, were rare or absent in farmland habitats, indicating that they find it especially difficult to adapt to farmland habitats.
In farmland habitats, we found that butterfly abundance increased with increasing flower species richness, and that increasing agroecological soil management practices increased the abundance of rarer species.
What does it mean?
Our research shows the potential of agroecology for mitigating some of the negative effects of woodland loss on butterflies. Encouraging smallholders to implement agroecological soil practices and increase the diversity of flowering crops (or perhaps tolerating some weeds) is an important contribution to butterfly conservation on farms.
However, maintaining woodland habitats was essential for conserving species richness with a variety of traits, and on-farm activities could not compensate for habitat loss at a landscape scale. Therefore, we call on stakeholders in the Miombo woodland ecoregion to increase conservation efforts of this unique habitat.
Read the full article “Local and landscape scale woodland cover and diversification of agroecological practices shape butterfly communities in tropical smallholder landscapes” in Journal of Applied Ecology
