Can drones help root out invasive plant species on the Galápagos Islands with the same effectiveness they eradicated rats that had threatened native birds with extinction? That’s what the Charles Darwin Foundation is hoping in deploying aerial assets to combat blackberry, guava, and other flora that now risk crowding out indigenous species.
That effort by the Charles Darwin Foundation begins with aerial mapping of highland areas of several Galápagos Islands, particularly Santa Cruz. Pilots fly DJI Inspire 1 and Mavic Pro drones over expanses of growth to collect geo-referenced, highly detailed imagery of plant life that – with the help of satellite photos – enables full mapping of various species.
The resulting models are used to study where and how fast invasive flora is growing, and vastly diminishing the presence of native plants like Scalesia pedunculata and Miconia robinsoniana as it does.
“The Scalesia forest on Santa Cruz has been reduced to only 3% of its original distribution, and every year we are losing about 5% of the current distribution to the blackberry,” explains Charles Darwin Foundation ecologist Heinke Jäger.
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The project follows an earlier and ultimately successful deployment of drones on two Galápagos Islands whose native bird species had been threatened by the proliferation of invasive rats. That two-step campaign began in 2019, first using drones to identify areas where the rodents were most abundant, then deliver reserves of specially developed rodenticide that only attracts rats.
In the second phase, UAVs were used to replenish bait stations in coastal areas, which were designed to eliminate both surviving rats and any swimming over from neighboring islands. Full eradication was declared in June of last year.
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The Charles Darwin Foundation is now hoping for a similar result against invasive plants spreading across the Galápagos Islands.
Blackberry and other introduced flora like Cuban cedar and guava grow faster than threatened native plants, occupying terrain and obscuring the sun that Scalesia and other indigenous species need to grow. Manual efforts to eradicate the invasive growth has been ineffective in stopping their spread, while chemical treatment has only had limited success.
Using images collected during drone flights, the Charles Darwin Foundation has created maps detailing the distribution and abundance of primary invasive and native plants in surveyed areas, as well as and key endemic species. Additional missions have documented changes in the plant composition and coverage, and – after comparison with earlier satellite shots – provide an idea of how fast changes to earlier balances have taken place.
It is hoped that use of drones to map location and spread of the destructive plants – and testing of methods to control their growth in native countries – can eventually be used to create an effective, targeted eradication approach that will provide indigenous species the space needed to stage their comeback.
“The biggest challenge is to find a solution that includes a biological control agent for these invasive species,” Danny Rueda, director of the Galápagos National Park Directorate.