Authors' Names

Tyler James ClarkFollow

Presentation Type

Oral Presentation

Category

STEM (science, technology, engineering, mathematics)

Abstract/Artist Statement

During the Anthropocene, human-induced extinctions, especially of large predators and herbivores, have resulted in catastrophic ecosystem collapses. Recently, conservation tools such as rewilding (e.g., re-introducing a species to its native habitat) have been used to mitigate the effects of extinction. Another increasingly popular conservation tool, ecological replacement, proposes to introduce functionally similar, non-native species to fill the ecological roles of extinct, native species, thereby restoring ecosystems towards their pre-Anthropocene state. For example, the non-native Aldabra giant tortoise was introduced to the Mauritian island of Ile aux Aigrettes to replace the ecological role of extinct Cylindraspis giant tortoises. However, the use of these tools is controversial, not least because it is difficult to predict the effects of species introduction. Furthermore, inferring the ecological functions of species that were driven to extinction 100s to 1000s of years ago is a major obstacle. Many species, including predators, impact ecosystems through their diet, so one way to test ecological replacement is to compare how the diets of non-native potential ecological replacements overlap with those of their extinct counterparts. Stable isotope ratios in the tissues of predators reliably predict what those predators are eating, therefore isotopic diet overlap between modern and historical tissue samples could test the effectiveness of ecological replacement as a conservation tool. Stable isotopes are elements with the same number of protons but different numbers of neutrons, which are integrated into tissues (e.g., bones, feathers, hair) from food consumed. In food available to predators, stable isotopes of carbon-13 increase from terrestrial to marine food sources, and isotopes of nitrogen-15 increase up the food chain in food sources. To exemplify this approach with stable isotopes, we tested whether non-native South American grey foxes (SAGF) act as de facto ecological replacements for extinct Falkland Islands wolves (FIW). Prior to their extirpation by man, the FIW was the only native terrestrial predator and land mammal inhabiting the Falkland Islands, South Atlantic. SAGFs were introduced to the Falklands in the 1920s for fur farming but rapidly became feral. Due to their impact on native birds and farmed sheep, they have been eradicated from three islands in the Falklands, with complete eradication being suggested. However, if SAGFs act functionally like FIWs, the Falklands ecosystem could be closer to its pre-Anthropocene state with them than without. We therefore measured stable isotopes in 32 hair samples collected from SAGFs on Weddell Island, Falklands, and in hair samples of FIWs from 8 of 9 known specimens held in museums throughout the world. We found that the stable isotope values of modern SAGFs almost completely overlaps that of extinct FIWs. Our results indicate that SAGFs could act as unintended ecological replacement for FIWs. Given the burgeoning interest in ecological replacement as a conservation tool, our technique is one way in which this method can be assessed objectively and quantitatively. Without these techniques, it is unclear if these conservation tools can adequately restore degraded ecosystems to their pre-Anthropocene state.

Mentor Name

N/A

Personal Statement

Researchers at the University of Montana and the people of Montana have a long history of studying, preserving, and re-introducing wildlife. Examples in Montana include the re-introduction of wolves in Yellowstone, the re-introduction of fishers, and the expansion of grizzly bear populations. In many ways, our state has led the way in developing these conservation tools. The conservation of wildlife, especially large predators, is one way in which Montanans exemplify their love for nature and all things wild. Lately, a conservation ethic known as “rewilding” has become popular. Rewilding is the idea to restore nature, places, wildlife, to their original state before the Columbian era. In fact, in the Spring 2020 semester, I developed and taught a class at UM on these topics (WILD 291: Rewilding Animal Populations, 2 credits). Many of these ideas have been tested in Montana (e.g., restoring wolves and their effect on elk, beavers, songbirds, and rivers). One rewilding technique gaining traction is ecological replacement, which is the idea that a non-native (i.e., invasive) species can replace the role of a species driven to extinction. Obviously, this is hard to test since many extinct species were lost 100s to 1000s of years ago, but as explained in the Abstract, we have found a way to test this conservation tool using stable isotope analysis. The importance of the work is that ecological replacement and other rewilding strategies are becoming increasingly popular, and subsequently used throughout the world. However, many have been critical of these strategies as they are exceedingly difficult to test, and introducing non-native species is known to have devastating effects on nature (e.g., invasive zebra mussels in lakes throughout Montana). My technique provides policy makers, including those in Montana, with much needed quantitative evidence to consider and use ecological replacement as a tool. Besides the practical elements of this tool, my work is important because it tells a vibrant story about our relationship with nature. The story of how the Falkland Islands wolf, whose extinction was predicted by Charles Darwin, was accidentally replaced by a non-native fox, is both intriguing and accessible. Given my results, I ask whether non-native foxes established in the Falklands should be maintained to replace the role of extinct Falkland Islands wolves. Foxes are bad for sheep farming and wild bird populations. But foxes also generate income via wildlife tourism and could maintain the ecosystem in a more “natural” state than if they were eradicated. My study cannot resolve the debate on how and why we value wildlife, native or introduced, but it can provide much needed evidence and dialogue to move the debate forward. Given the necessity of current debates about our relationship with nature, I believe my work should be considered for the Best of GradCon award, given its relevance to our community at the University of Montana and Missoula, throughout Montana, and humanity.

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A wolf in fox’s clothing? Using stable isotopes to quantify ecological replacement

During the Anthropocene, human-induced extinctions, especially of large predators and herbivores, have resulted in catastrophic ecosystem collapses. Recently, conservation tools such as rewilding (e.g., re-introducing a species to its native habitat) have been used to mitigate the effects of extinction. Another increasingly popular conservation tool, ecological replacement, proposes to introduce functionally similar, non-native species to fill the ecological roles of extinct, native species, thereby restoring ecosystems towards their pre-Anthropocene state. For example, the non-native Aldabra giant tortoise was introduced to the Mauritian island of Ile aux Aigrettes to replace the ecological role of extinct Cylindraspis giant tortoises. However, the use of these tools is controversial, not least because it is difficult to predict the effects of species introduction. Furthermore, inferring the ecological functions of species that were driven to extinction 100s to 1000s of years ago is a major obstacle. Many species, including predators, impact ecosystems through their diet, so one way to test ecological replacement is to compare how the diets of non-native potential ecological replacements overlap with those of their extinct counterparts. Stable isotope ratios in the tissues of predators reliably predict what those predators are eating, therefore isotopic diet overlap between modern and historical tissue samples could test the effectiveness of ecological replacement as a conservation tool. Stable isotopes are elements with the same number of protons but different numbers of neutrons, which are integrated into tissues (e.g., bones, feathers, hair) from food consumed. In food available to predators, stable isotopes of carbon-13 increase from terrestrial to marine food sources, and isotopes of nitrogen-15 increase up the food chain in food sources. To exemplify this approach with stable isotopes, we tested whether non-native South American grey foxes (SAGF) act as de facto ecological replacements for extinct Falkland Islands wolves (FIW). Prior to their extirpation by man, the FIW was the only native terrestrial predator and land mammal inhabiting the Falkland Islands, South Atlantic. SAGFs were introduced to the Falklands in the 1920s for fur farming but rapidly became feral. Due to their impact on native birds and farmed sheep, they have been eradicated from three islands in the Falklands, with complete eradication being suggested. However, if SAGFs act functionally like FIWs, the Falklands ecosystem could be closer to its pre-Anthropocene state with them than without. We therefore measured stable isotopes in 32 hair samples collected from SAGFs on Weddell Island, Falklands, and in hair samples of FIWs from 8 of 9 known specimens held in museums throughout the world. We found that the stable isotope values of modern SAGFs almost completely overlaps that of extinct FIWs. Our results indicate that SAGFs could act as unintended ecological replacement for FIWs. Given the burgeoning interest in ecological replacement as a conservation tool, our technique is one way in which this method can be assessed objectively and quantitatively. Without these techniques, it is unclear if these conservation tools can adequately restore degraded ecosystems to their pre-Anthropocene state.