Combating Invasive Species: Protecting Galapagos Wildlife and Ecosystems

September 22, 2017

By guest author Dr. Heinke Jäger, Restoration Ecologist at the Charles Darwin Foundation.

Scalesia

Endemic Scalesia pedunculata (© Heinke Jäger)

I first arrived in Galapagos in 1996 as a tourist. I’d been working in agricultural research for 8 years before studying biology, so I was intrigued to learn about agricultural challenges around the world. With this in mind, I headed up the trail to Media Luna on the island of Santa Cruz, where the only person I met along the way was a farmer. Despite my limited Spanish, we managed to have a decent conversation. I learned that invasive species, particularly common guava and quinine, were rampant on his farm, making it difficult to produce agricultural crops and costing a lot of money to control. In the final stages of my biology degree, I had my “light bulb” moment about working on the quinine tree Cinchona pubescens.

I was thrilled when I received an offer from the Charles Darwin Research Station (CDRS) to work on the impacts of quinine on the vegetation in the highlands of Santa Cruz. I returned to Galapagos for what was supposed to be one year in January 1998, but the islands and CDRS have kept me captivated for almost 20 years now! With the help of Dr. Alan Tye, then head of the CDRS Botany Department, and many CDRS volunteers, we established 30 large (400 sq m) plots in the fern-sedge vegetation near the very top of the island and another 30 plots in the Miconia zone (a relatively limited zone below the fern-sedge zone, dominated by the endangered endemic shrub Miconia robinsoniana). These plots laid the foundation for several long-term studies on quinine, including its impacts on soil and vegetation, and the impacts that quinine control actions have on non-target species. This work was originally funded by a grant from the European Union and is now supported by GC.

Invasive blackberry

Invasive blackberry, Rubus niveus (© Heinke Jäger)

From 2000 to 2005, I worked on endangered endemic and native species, many of which were threatened by invasive plant and animal species. These years provided a fabulous opportunity to get to know many of the uninhabited islands, and gave me a deep appreciation of the unique and amazing flora and fauna of the beautiful Galapagos Islands. The challenge of understanding the ecology and impacts of invasive species continued to fascinate me and, with the help of GC, we have added several other introduced plants to the list of target invasive species, like blackberry (Rubus niveus), sauco (Cestrum auriculatum) and Wandering Jew (Tradescantia fluminensis), as well as invasive animal species, like the tropical fire ant (Solenopsis geminata) and the treefrog (Scinax quinquefasciatus).

In 2013, CDRS — along with the GNPD and ornithologists working with Dr. Sabine Tebbich at the University of Vienna — began a project to evaluate the impacts that the more than 10 years of control actions by the GNPD to combat the invasive blackberry (using both manual and chemical methods) have had on the native vegetation, invertebrates, and birds at Los Gemelos in the highlands of Santa Cruz Island. This area contains the last remnant of the once common Scalesia forest, dominated by the endemic giant daisy tree Scalesia pedunculata. The forest is now reduced to only 100 ha, as a result of past agricultural activities and, more recently, by invasive plant species, predominantly blackberry. The goal of the current project is to develop a holistic long-term plan for the sustainable management of the Scalesia forest ecosystem.

Monitoring at Los Gemelos

A monitoring plot at Los Gemelos (© Heinke Jäger)

We are currently monitoring 34 large (100 sq m) permanent plots in areas where blackberry was controlled and in areas still heavily invaded by blackberry. Together with my Galapagueño field assistant, Marcelo Loyola, I carry out the vegetation monitoring while the CDRS entomologist, Jacqueline Rodriguez, and assistants carry out the invertebrate surveys. The Austrian ornithologists and their Ecuadorian students carry out the assessment of bird density and breeding success, with a special focus on the endangered green warbler finch and the small tree finch. Initial results indicate that the control efforts have been successful in reducing blackberry cover and that after an initial decline, the native vegetation, invertebrate, and bird populations did recover. However, given how dry the last two years have been, it is difficult to separate the impacts of blackberry and its control from that of the recent drought.

Climate change is predicted to increase rainfall in the Galapagos Islands, which will probably exacerbate problems caused by invasive species. Therefore, it is indispensable to study invader impacts in long-term plots to disentangle the effect of the invader (and its control) from that of a changing climate. Thanks to the support of GC, we are now able to do just this, not only at Los Gemelos, but also in the Media Luna area, where, since 2013, we have continued monitoring the permanent plots to study the long-term impact of quinine on the native vegetation. We have also assessed the impacts that manual and chemical control of quinine, which the GNPD has carried out in some of the plots since 2003, has had on non-target species. Unfortunately, these control actions appear to be facilitating the blackberry invasion. Therefore, our recommendation to the GNPD is that quinine control should only be initiated when continuous follow-up control of the re-sprouting quinine and blackberry is possible.

Monitoring at Media Luna

The author (right) and field assistant Marcelo at the Media Luna site (© Lorea Cardas)

Complementary studies on invasive species include work on the tropical fire ant led by CDRS scientist Dr. Charlotte Causton, and research on the invasive tree frog and the mapping of dominant plant species, led by CDRS spatial analyst MSc. Carolina Carrión. Stay tuned for future updates on these projects!

Heinke_BioPhotoHeinke Jäger has been working at CDRS since 1998 on countless research projects involving introduced species such as quinine and blackberry and also on many rare and endangered plant species. After receiving her PhD from Technical University Berlin, Germany, she carried out her postdoctoral research on invasive species at Brown University, USA. She is now a Restoration Ecologist at CDRS and her research is focused on investigating terrestrial plant and animal species in Galapagos, which includes the distribution, impacts and control of these species, as well as the restoration of invaded ecosystems.

Galapagos Conservancy has been supporting the Charles Darwin Foundation’s Invasive Species project since 2011.

Read more about managing invasive species in Galapagos.

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