Cape Town – Gum trees, regarded in South Africa as bad aliens that invade indigenous vegetation and suck up huge amounts of scarce water, have an indirect but crucial role to play in South Africa’s food production.
A recent study by the SA National Biodiversity Institute (Sanbi) has found that gum trees provide nectar and pollen for swarms of commercial bees – and bees in turn pollinate about 50 food crops in the country.
This “service” bees provide is worth about R10.3 billion a year. Sanbi researchers Mbulelo Mswazi and Carol Poole say gum trees are not only important food for bees, but so are many roadside wildflowers, crops, suburban flowering plants and those that many regard as weeds.
They say a major reason for the decline of honey bees around the world is a lack of good forage plants to provide nectar, which is the carbohydrate in the bees’ diet, and pollen the protein.
“A lack of good quality and variety of forage plants can lead to unhealthy honey bee colonies that are more vulnerable to pests and diseases.
This in turn can lead to insufficient pollination of our important agricultural crop flowers, leading to a decreased yield or quality of the food crop,” they said. Insect pollinators are needed for 35 percent of all food production globally – or one of every three bites you eat.
Mswazi and Poole say because beekeepers are highly dependent on eucalyptus, if they are all removed because they are aliens it would mean a serious shortage of food for bees – with a knock-on effect on crop pollination.
Because of this, the Department of Environmental Affairs’ legislation on alien and invasive species, updated last year, is “nuanced” for eucalyptus trees, not requiring all of them to come under the axe or chainsaw.
Gum trees in streams, in protected areas such as nature reserves and in ecosystems identified for conservation purposes, should be cut down.
There are six species the legislation defines as invasive, which have to be controlled even outside these areas.
The researchers say because beekeepers are highly dependent on gum trees, and because the removal of all gums would result in a severe shortage of forage for bees, landowners ought to make sure the gums they cut down are those required to be removed under the Alien and Invasive Species Regulations, promulgated under the National Environmental Management Biodiversity Act.
Guy Preston, a deputy director-general in the department, said it had worked closely with the commercial bee industry when developing the regulations. It understood that commercial beekeepers needed a source of food from gum trees.
“We focused on invading gums in the legislation – there is no question that those have to go.
The beekeepers agree on that. Only six are a real problem. Some are very fire-prone, so we don’t want them in areas at risk of fire,” Preston said.
“Blue gums are one of the invasives which are a problem, but it depends on where they are. A group of blue gums around a Free State farmhouse surrounded by wheatfields have nothing to invade into.”