By Dr Aoife Delaney
Pollination is a great example of how, in ecology, everything is connected. Plants depend on insects to reproduce and insects depend on plants for food. By supporting each other, plants and insects support a lot of other organisms which live on or in them. Accordingly, many of the best conservation projects take an integrated approach to protecting ecological systems. The project I am currently working on as a post-doctoral researcher with Prof. Jane Stout is a good example: assessing the impacts of landscape structure on pollination services in Burkina Faso, West Africa.
Nicknamed “Trees, Bees and Butter”, this project is a collaboration between BirdLife International and their partner in Burkina Faso, Naturama, the Royal Society for the Protection of Birds (RSPB), Trinity College Dublin and the University of Ouagadougou. It is part of a larger, Darwin Initiative- funded project in which The Society for the Protection of Birds in the Netherlands (VBN) and the Global Shea Alliance are also partners. Given the prominence of BirdLife, the RSPB and VBN it is not surprising that bird conservation was the original driver of the work, so why have I focussed on bees and pollination?
Sharp declines in migrant bird populations in Europe over two decades raised concern among bird conservationists. When they investigated, they found that there could be problems in the wintering grounds in West Africa, where scrub and forests have been cleared for agriculture and fallow areas have become smaller and shorter-lived. Only the fruit-bearing trees remain dotted through the fields. Similar trends have been associated with wildlife losses elsewhere, and they are difficult to reverse because farmers need to make a living. However, if conservation friendly land-uses are shown to benefit local farmers, it might be possible to manage land better for people and for nature.
This is where pollination comes in. Pollinating insects in West Africa depend on flowering trees as a source of food and shelter. When an area is cleared of most of its trees, leaving only species of economic importance, the resources available to pollinators are restricted and their populations might fall. The remaining trees could struggle to find pollinators for their flowers, in which case fruit yield of pollinator-dependent trees would fall after scrub clearance. Pollinator-dependent fruit trees include shea (Vitellaria paradoxa) which is common in West African shea parklands and is economically valuable due to the growing use of shea butter in cosmetics and confectionary.
We wanted to find out whether pollination services to shea are affected by changes to farming practices in shea parkland in Burkina Faso. To do so, we first chose sites in areas which had different amounts scrub and fallow land near Kabore Tambi National Park. Then we counted the insects visiting shea flowers to see whether sites with different landscape structures had different numbers or species of flower visitors. We also estimated the effectiveness of flower visitors as pollinators by saturating some sets of flowers with pollen and leaving others open for insects to pollinate. The number of fruits yielded by pollen-saturated flowers tells you the maximum amount of fruit you can expect if everything that can be pollinated is pollinated. The fruit yield of open flowers tell you whether pollination services are close to delivering this maximum pollination potential, or are much lower.
As shea only flowers for a few months each year, we wanted to know what other resources were important to pollinators in shea parklands, so we also recorded other flowering tree and shrub species in our sites, and what was visiting them.
It is too early to talk about results just yet, but we did make some interesting observations in the field. Many of the less profitable native trees and shrubs remain in the fields but do not produce flowers as they are cut back or browsed frequently. Their persistence in the landscape represents a potential future resource for pollinators. Most of the pollinating insects we observed were tiny wild bees, much smaller than a honey bee. Ensuring that these wild bees have access to nest sites might be an important part of securing pollination services. As well as bees, we found a wide range of other insects in shea flowers – flies, ants and bugs in particular. Although they might not act as pollinators, this demonstrates that shea trees are likely to house food for insectivorous birds such as the willow warbler. Encouragingly, many village chiefs and local farmers were interested in finding out about nature friendly farming.
Nature in West Africa is under pressure as climate change and human population growth make themselves felt. Compared to other parts of the world, agricultural intensification started relatively recently, and non-commercial species persist within cultivated areas. If we act now and show that conservation of natural habitats can benefit agricultural communities, we could help Africans to achieve what Europeans have failed to do: develop farming methods which are good for people and the planet. This seems like great expectations of a little project, but whatever my findings are, they will shed a light on a type of agriculture which is spread over more than a million square kilometres, supports tens of millions of farmers, and is changing rapidly.
This project is funded by the UK Government’s Darwin Initiative: a grants scheme that helps to protect biodiversity and the natural environment through locally based projects worldwide.
About the author: Aoife Delaney is a post-doctoral conservation scientist at RSPB, working with Prof Jane Stout at Trinity College Dublin on shea pollination in West Africa.