Galapagos Invasive Species:
Noxious weeds

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War on quinine: The quinine tree invasion - its long-term impact and management

Quinine on PuntudoThe quinine tree Cinchona pubescens is one of the most serious alien plant invaders of the Galapagos Islands and is characterised by vigorous growth and reproduction and extremely rapid invasion. Originally introduced in 1946 in the agricultural zone of Santa Cruz island, quinine has spread into all the highland vegetation zones (Scalesia, Miconia and Fern-Sedge Zones) and today covers more than 12 000 ha. Quinine is considered a “transformer”, changing the plant species composition and community structure of the highlands of Santa Cruz. The increasing presence and density of quinine in the highlands of Santa Cruz near Cerro Crocker has been recorded photographically from 1975, 1990 and 1998.

This is the opposite extreme of invasive species management research from our experimental eradications. How do we manage a well-established, widely-distributed invader? In spite of the obvious impact of quinine on the native vegetation, until recently its ecology had hardly been studied and no effective control techniques had been found. The Charles Darwin Foundation began a series of studies in 1998 to investigate its ecology and invasion dynamics, its impact on the native vegetation and soil structure, and methods of control. All these studies are essential precursors to designing an effective management plan.

So far, studies carried out by Heinke Jäger have shown that quinine is significantly reducing the native vegetation. Research on its biology by student Jorge-Luís Rentería has shown that seed production is high, with high viability for fresh seeds, but the seeds are not often dispersed far, nor do they survive long in the soil.

In 2000, control trials finally identified an effective combination of control techniques. “Hack-and-squirt” application of picloram plus methyl metsulphuron herbicide into machete cuts on the trunk killed most trees in experiments, while saplings are easily pulled out of the ground by hand. This combination of methods is now used for routine control by the GNP. By monitoring vegetation before and after control, we also assess the success of control and the impact of control on the native vegetation. Finally, we are gathering data on the costs of control at different quinine densities in different hábitats, to feed into our eradication feasibility model.

All these data will allow us to draw up a long-term management plan for the species in Galapagos and help us decide whether we can attempt total eradication with a reasonable chance of succeeding.

Source: Charles Darwin Foundation.

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This website was created on 25 October 2004 by PT and JK