Let’s Bee Real: Forest Management Is Critical for Pollination Services
This post is written by Gabriela Wiederkehr, Smitha Krishnan, Christopher Kettle, Alliance Bioversity-CIAT.
Pollinators play a vital role in transferring pollen from one plant to another to allow the process of fertilization and therefore the production of seeds. An estimated 87.5 percent (94 percent in the tropics and 78 percent in the temperate zones) of wild flowering plants globally are animal-pollinated. When speaking of pollinators, the focus often falls on a few bee species, mainly those that are managed (e.g. honeybees) as they are preferred to sustain large production systems, overlooking the wide diversity of pollinators. However, wild pollinators such as wild bees, butterflies, hoverflies, wasps, and other non-insect pollinators (birds and mammals) provide important pollination services, not only for cultivated plants (often complementing managed pollinators) but also for wild plants; and they are imperative for the conservation of biodiversity and the maintenance of associated ecosystem services.
Globally, more than 70 percent of food crops benefit from animal pollination (with dependence for fruit set or seed set ranging from 1 percent to 100 percent). Several studies have demonstrated the importance of wild pollinators in increasing crop fruit set, pointing out the vital role they play, and the contributions of such wild pollinators cannot be substituted by managed bees. Many of these wild pollinators depend heavily on forests for nesting and food, and the area covered by forests and other natural habitats in a landscape plays a role in determining the diversity of species present in an area. Agricultural lands' adjoining forests or natural areas benefit from pollinator services since animal-pollinated crops can achieve higher fruit set. The proportion of wild habitat required to provide such additional pollination services for crop plants may differ by crop type and other landscape variables. Therefore, management practices at a landscape scale are vital to ensure the continued availability of pollinators and thereby increase resilience and the productivity of forests and agriculture. This includes the long-term productivity of many non-wood forest products (NWFP) that are important not only for local livelihoods but also local to national economies.
Factors that influence wild pollinators
Scientists globally have been raising concerns about declines in pollinator populations for more than three decades due to the impacts of forest management practices, landscape-scale changes, and climate change. For example, at a landscape scale, the composition of a landscape is likely to have significant implications for the floral and nesting resources of pollinators and therefore their presence and abundance. Land-uses change, and land management practices fragment and degrade pollinator habitats and consequently affect how pollinators are able to move within a landscape. They both are major drivers of pollinator declines. Maintaining connectivity among fragmented habitats is important, to facilitate movement of pollinators between patches.
Likewise, forest management practices can also have significant effects on pollinator abundance and diversity. For example, logging affects forest variables — such as structure, soil dynamics, water regulation, and light availability — which affect plant and pollinator species composition and associated plant-pollinator interactions. Mowing removes flowers and, thus, the food sources of pollinators which influences pollinator diversity and abundance. And the introduction of invasive alien plants can alter the species composition of pollinators which in turn could impact pollination of native plants and plant-pollinator networks.
Climate change also plays a key role as it may affect flowering events, fruit maturation, leave unfolding, and plant-pollinator interactions in general. For example, a decrease in synchrony between the unfolding of leaves in a host plant and the larvae of a herbivore pollinator may reduce the density of the pollinator population.
Safeguarding pollination services
To safeguard pollination services, pollinator-friendly management is needed at the forest and landscape scale. Adapt pollinator-friendly agricultural systems to enhance native pollinators to reduce the dependence on managed bees or other alternatives to animal-pollination (such as hand pollination). The recently published FAO review on pollination services lists a set of proactive measures for forest and landscape managers that could help in safeguarding pollinators (see Chapter 5 of the report for the full list of recommendations). The measures are drawn from the findings of a review of existing literature and expert-validated feedback. Note, however, that the most effective means for conserving pollinators are likely to be highly specific to local conditions, and ongoing research, monitoring and adaptive management will be essential.
At the landscape scale, some of the measures are, among other things:
- Landscape-scale planning to maintain key landscape components on which pollinators depend;
- Ensuring habitat connectivity, including through agroforestry, creating biological corridors or stepping stones within a hostile matrix habitat, and retaining native vegetation;
- Enhancing the density of floral resources;
- Maintaining or increasing landscape heterogeneity and patchiness to increase the diversity, and connectivity of floral and pollinator-nesting resources; and
- Maintaining large riverine buffers; and undertaking long-term studies to understand the impacts of natural and man-made disturbances on pollinator communities over time.
Forest Management Scale
At the forest management scale, the measures may include:
- Establishing baselines of pollinator diversity and abundance and monitoring these over time;
- Developing field guides for pollinator management based on knowledge of the biological attributes of pollinator species in an area (nesting and forage);
- Employing forest management practices such as selective logging, thinning, prescribed burning, mowing and coppicing in ways that increase the plant and insect diversity; and,
- In restoring degraded forests, establishing tree species at densities sufficient to enable their effective pollination.
Beyond the natural: Politics and multi-sectoral involvement
Most importantly, the impacts of landscape and forest management on pollinators should be addressed multi-sectorally, with the involvement of farmers, pastoralists, indigenous peoples, local communities, forest managers, beekeepers, and other land custodians and stakeholders.
Policy instruments are needed that encourage practices in the forest and agriculture sectors to help maintain and increase pollinator services, especially given the potential impacts of climate change. These may include mechanisms to facilitate exchanges of knowledge among stakeholders in the forest and agriculture sectors and to help determine trade-offs between interests and ecosystem services; payments for pollination services and other economic incentives to support pollinator-friendly landscape management; and comprehensive guidelines for ensuring the maintenance of pollination services in forests and landscapes. Evaluations of the economic benefits of wild pollination, the economic consequences of its decline and the cost of pollination management could help in making an informed decision by weighing the loss and gains.
All in all, arguments about biodiversity conservation, ecosystem resilience and food security might not always be sufficient to ensure that actions are taken to improve pollination services. An integrated approach involving science, policy, farmers, and forest and landscape managers is needed to lift the buzz off pollination services.