Drones used to control invasive blackberry, guava plants on Galapagos Islands

By Susana Madera

Santa Cruz Island, Ecuador, May 9 (EFE).- Blackberry and guava add flavor to a range of dishes and are ingredients in exotic desserts but they also pose a mortal threat to endemic species on Ecuador’s Galapagos Islands, where scientists have deployed drones to track those and other invasive plants and check their spread.

They are turning to those aircraft and to satellite imagery in a search for answers about the approximate reach of invasive species, the magnitude of the task required to control them and whether any plant species compositions promote or limit the habitat range of threatened fauna.

Those technologies also are being employed to map important endemic plant species such as Scalesia pedunculata and Miconia robinsoniana, and thereby are playing a key role in ecosystem restoration efforts.

NEARLY EXTINCT FORESTS

The genus Scalesia encompasses 15 species, including three trees that can grow to heights of almost 15 meters (49 feet) and shrubs which are found in arid zones and emit a fragrant aroma.

Although Scalesia forests can still be observed in higher elevations of Santa Cruz Island and other parts of the Galapagos archipelago, Heinke Jager, a German restoration ecologist with the Charles Darwin Foundation, told Efe that agricultural activities of the past and invasive species, especially the blackberry, have exacted a heavy toll.

“Of what we had, only 3 percent is left,” she said.

But now, in tandem with the Galapagos National Park Directorate (DPNG), scientists are trying to “rescue this Scalesia (forest) from extinction” on Santa Cruz.

The work is focused on a 300-hectare (740-acre) patch of forest, all that is left of a previous expanse of 10,000 hectares.

BLACKBERRY: THE BIGGEST MENACE

The blackberry was introduced into the archipelago in 1968 and has become the main threat to endemic species, said Jager, who earned her doctorate from the Technical University of Berlin and carried out postdoctoral research on invasive Galapagos species at Brown University,

That thorny, climbing shrub is competing for space with the Scalesia plants, she said, adding that it “makes a lot of shade and doesn’t allow (those species’ seeds) to grow.”

Besides being endemic to that Pacific Ocean archipelago, located around 1,000 kilometers (620 miles) off the coast of Ecuador’s mainland, the Scalesia trees and shrubs are important because of their many associated species.

Insects live in the lichens and mosses that grow on their branches and serve as food for Darwin’s finches and other birds.

And just as there are insects that only feed on Scalesia plants, their disappearance could lead to the extinction of certain types of moths, for example.

MANUAL AND TECHNOLOGY-AIDED WEED CONTROL

In an attempt to keep the invasive blackberry in check, DPNG rangers cut away that plant pest manually and then apply herbicides, although the effort seems interminable.

“In an experimental 14-hectare area, we’re been combating the blackberry for eight years and it keeps regenerating itself,” Jager said.

The task of containing the spread of blackberries is a titanic one for two reasons: many of their small seeds remain in the soil, while others are dispersed over a wide area through the droppings of birds and other animals that eat the plants’ fruit.