Bees boost Brazil’s forest restoration, scientists say

“Restoration programmes have the power to bring back bee populations, just as bees may stimulate the reproduction and resilience of native species in degraded ecosystems,” – RICARDO RIBEIRO RODRIGUES, COLLEGE OF AGRICULTURE, UNIVERSITY OF SÃO PAULO

31/01/20 –

Researchers looked at how bees can boost pollen dispersal during tree planting projects in Brazil. Researchers looked at how bees can boost pollen dispersal during tree planting projects in Brazil. Copyright: Jon Sullivan [Public domain image].

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  • Bee conservation should be priority in forest restoration projects: study
  • Bees are crucial pollen transporters for diverse tree species
  • Their number increases where forests have been restored

By: Rodrigo de Oliveira Andrade

[SÃO PAULO] Some of the most important tree species for the restoration and conservation of tropical forests rely heavily on bees as transporters of pollen.

Bees facilitate pollination over great distances, increase the genetic diversity of plants, and stimulate the reproduction and resilience of native species in degraded ecosystems.

That’s why conserving these declining insects should be a priority in forest restoration projects, according to a study by Brazilian scientists published in Ecological Applications.

The study analysed how different bee species responded to changes in Brazilian forest landscapes. It investigated how increasing bee populations may boost pollen dispersal when planting trees in restoration projects, and also help re-establish diverse forests in disturbed areas in Brazil.

Researchers carried out fieldwork in an agricultural area of the Atlantic Forest in the country’s south-east, which had been turned into sugarcane fields. Only about seven per cent of the original vegetation remains there, in small fragments of primary forest comprised of discontinuous canopies covered by vines and bordered by invasive grasses.

The team also included two other less degraded areas as reference ecosystems. One of these contained contained highly diverse trees reintroduced by researchers about two decades ago to increase forest cover, while the other consisted of wetlands, dominated by herbaceous vegetation.

In each of these landscapes, researchers installed “pan traps” — a standard method for capturing bees — with the aim of collecting insect samples at the peak of the flowering season, between October 2015 and January 2017.

They compared the abundance and diversity of bee populations in each habitat and analysed the pollen grains stuck to their bodies to determine which plant species the insects had interacted with.

The team collected 727 bees of 85 species, with different sizes and flight skills, social behaviour, nesting sites and diets, and found that these had interacted with 220 different plant species.

The abundance of bees responded negatively to habitat change, decreasing in highly disturbed environments — such as anthropogenic wetlands and sugarcane fields. But their number increased in areas where forest had been restored, as well as in original forest fragments, where large and medium-sized species that nest above-ground were predominant.

Small and medium-sized bee species that nest underground, with varying levels of social behaviour and diet, were unaffected by habitat change, and even tended to increase in some disturbed areas, researchers said.

Meanwhile, ‘oligolectic’ bees — which typically prefer pollen from a single genus of flowering plants — responded negatively to habitat change.

Author: Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

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