One of the biggest threats to many species caused by human is global warming. It is a result of human burning fossil fuel, thus increasing the amount of carbon dioxide in the air. Certain species can only survive under specific range of temperatures. However, as the climate continues to increase, many species are facing potential possibilities of extinction.
At the beginning of the chapter five of the book Rambunctious Garden, Marris gives an example of how global warming affects certain species. As the climate keep getting warmer, American pikas have to move to the top of the mountains to stay cooler. However, for some of them who are already at the top of the mountain, they have nowhere to go. “The animal could never migrate on its own; the trip down to the lowlands to get to the next mountain would kill it (Marris 106).” Scientists feel that human have the responsibility to clean up the mess that they produced; therefore, they came up with the idea of assisted migration, which is basically moving species to a place before it gets too warm. As human are burning more fossil fuels to become powerful, the concentration of carbon dioxide in the atmosphere raises dramatically, as a result; the temperature increases every years. It becomes harder for plants and other animals to live in this heated world. According to scientist many plants and animals can only live within certain range of temperature and climate patterns, therefore a lot of them are expected to move to other places. Assisted migration seems like a very good idea, it is somewhat similar to the concept of rewilding, which is the idea of reintroducing similar species into an area, and to restore ecosystem back to 10,000 years ago, before human intervention. Marris talks about two different type of migration. The first one is upward migration, which is simply moving species up to the top of the mountain, to help them stay cooler. “Many range shifts for individual species have already been documented. University of Exeter biologist Robert Jon Wilson found that in the Sierra de Guadarramas in central Spain butterfly ranges have shifted, on average, 200 meters uphill in the last thirty-five years (Marris 109).” Although research shows that species are already moving upward, the problem with that is when all the species are moving up, then there will be a great competition of food, space and air at the top of the mountain. Eventually some of the species live at the top of the mountain are going to be extinct. Not only there is upward migration, scientists also recorded the pole-ward migration. Data from the studies of butterflies suggests that these butterflies didn’t just move up, approximately 63 percent of them also move 20 to 150 miles north since 1900 (Marris 110).
Although assisted migration may temporarily save some endangered species from getting extinct, its long-term effect is still unpredictable. I don’t think assisted migration is a good idea to save the species from getting extinct because we have no idea how these species are going to behave in the new area. As some people argue, these species may become invasive ones, which may resulted in losing even more native species.
