Penn Sustainability Review Volume 1 Issue 9 Humans Article 7 2-21-2017 First Them, Then Us Rosie Nagele Follow this and additional works at: https://repository.upenn.edu/psr Part of the Environmental Studies Commons Recommended Citation Nagele, Rosie (2017) "First Them, Then Us," Penn Sustainability Review: Vol. 1 : Iss. 9 , Article 7. Available at: https://repository.upenn.edu/psr/vol1/iss9/7 This paper is posted at ScholarlyCommons. https://repository.upenn.edu/psr/vol1/iss9/7 For more information, please contact [email protected]. First Them, Then Us This article is available in Penn Sustainability Review: https://repository.upenn.edu/psr/vol1/iss9/7 WRITTEN BY ROSIE NAGELE FIRST THEM, TheTHEN human case for US biodiversity conservation The words “endangered species” often conjure up an image of a sleek, striped tiger slipping through a jungle or a human-related disasters, and protect against infectious muscled polar bear navigating a landscape of fractured disease.1 Loss of biodiversity, in turn, disrupts ecosystem ice. The idea of losing these beautiful and inspiring crea- stability, jeopardizing the processes that maintain the tures generates genuine feelings of distress and concern. resources that humans depend on. For example, species However, it also seems distant: tragic, yes, but without extinctions threaten food security both by directly elimi- direct repercussions to human life. After all, species ex- nating sources of food and by disrupting ecological pro- tinction is a natural process and the evolution of nature’s cesses that facilitate agriculture. Biodiversity has been complexity would be impossible without it. Amid the found to play important roles in nutrient recycling, mi- profusion of dire warnings about environmental change, croclimate regulation, detoxification of chemicals, and issues with clear impacts on human life, such as climate the suppression of pests, all of which are processes that change or fresh water pollution, often appear more de- influence crop yields.2 Additionally, species diversity is serving of our time and resources. However, there is an associated with greater stability of fishery yields, a food intimate relationship between the well-being of human- source that is rapidly increasing in demand.3, 4 ity and the diversity of species on our planet. Moreover, growing evidence of accelerated anthropogenic-induced Another element of ecosystem health is the provision of extinction has begun to reveal the precarious state of this clean water, which has become a serious issue to human relationship. Recognizing the tangible benefits that di- health as pollution levels increase. A study in the jour- verse species provide could be the key to ensuring that nal Ecology by Bracken and Stachowicz found ecosys- sufficient effort and resources are applied to protecting tems with greater species diversity to purify water more them. effectively than ecosystems with less.5 More recently, Na- ture published a study of algae in streams that identified Biodiversity, the variety of species in an ecosystem, is a niche partitioning as one potential mechanism for this critical element of maintaining a healthy environment beneficial effect.6 When more species are present, each for humans to live. Biodiversity contributes to an eco- species develops a specialized niche, which maximizes system’s ability to provide stable food sources, purify air the amount of compounds they can process. This find- and water of contaminants, protect against natural and ing directly links biodiversity to improved water quality. 48 | PENN SUSTAINABILITY REVIEW Furthermore, a 2012 study in BioScience found a direct times the background extinction rate.11 One of the main link between biodiversity and poverty relief.7 Although threats to amphibians is infection by a chytrid fungus, poverty alleviation is often associated with development which has spread dramatically due to human travel.12 that compromises biodiversity, analysis of the direct eco- The fungus, native to Africa, is suspected to have begun logical services and financial compensation provided by its global spread through the international trade of the healthy and diverse ecosystems found biodiversity con- frog Xenopus laevis, beginning in the 1930s.13 Subse- servation to actually reduce poverty and enhance human quent movement of amphibians and chytrid spores by well-being. humans has led this pathogen to become a threat to am- phibians worldwide.14 Like amphibians, birds are also ex- Although there is much evidence to support the im- periencing an elevated extinction rate, an estimated 100 portance of biodiversity to human life, further miscon- times greater than the background rate, which is large- ceptions exist over whether or not biodiversity really is ly a consequence of human development of forests and decreasing and, if so, whether human activity is respon- the ensuing destruction of habitat.15 Researchers have sible. As early as 1999, 70% of biologists expected that also identified a correlation between human population 20% of all species that then existed would die out within density and the proportion of threatened bird species 30 years due to human activity, but also considered the per country as well as between per capita GNP and the issue of extinction to be marginalized by the public, gov- proportion of threatened mammal species.16 All of these ernment, media, and educators.8 Since this survey, evi- results point to the presence and activity of humans as a dence for the acceleration of extinction rates and, more- major threat to biodiversity. over, humanity’s role in this shift, has grown. Extinction occurs continuously at a background rate, the rate that Even in cases where the global extinction rate of a spe- species go extinct due to individual interactions.9 How- cies is difficult to determine, data regarding local extinc- ever, other forces such as volcanic eruptions and mete- tion provides useful information.17 Species are said to be or impacts can increase the extinction rate significantly locally extinct when they are no longer present in a given from the background rate, causing mass extinctions.10 ecosystem but still exist elsewhere. Local extinctions of- Human activity is emerging as such a force. For exam- ten result in the disruption of the ecosystem, which can ple, a 2007 study in the Journal of Herpetology found the have negative impacts on human communities. A study current amphibian extinction rate to be 25,000 to 45,000 in Biotropica observed the local extermination of gorillas, PENN SUSTAINABILITY REVIEW | 49 ROSIE NAGELE chimpanzees, and three species of arboreal frugivores part, such as the ivory tusks of elephants. Overexploita- from hunting in Cameroon forest sites to reduce the seed tion is attributed to nearly a quarter of known extinctions dispersal of the tree Antrocaryon klaineanum.18 Anoth- in recent decades.27 One of the most notable examples of er study in the forests of Los Tuxtlas found that local extinction via overexploitation is the passenger pigeon. extinctions of medium and large mammals by hunting The passenger pigeon was one of the most abundant or habitat loss caused growth in the rodent population birds before humans began to hunt it, which, in conjunc- and a subsequent decimation of the small-seeded under- tion with habitat fragmentation, led to its extinction.28 story on which the rodents fed.19 Thus, human activity has been linked to increased levels of both global and Introducing non-native species also poses a threat to local extinctions, resulting in profound changes to the biodiversity as the exotics outcompete the natives for dynamics of species interactions and a disruption of the resources or decimate native populations via predation resources and stability of the ecosystem. or parasitism. For example, the extinction of many is- land-endemic birds is attributed to predators, such as The main ways in which human activities influence -ex rats, that were introduced by humans.29 As in the case of tinction are habitat destruction and degradation, over- the chytrid fungus, human travel and activity has trans- exploitation of plant and animal species, introduction ported numerous diseases to new populations, leading of non-native species, pollution, and global warming. their populations to severely decline, sometimes to the Many scientists consider habitat destruction the leading point of extinction. For example, the extinction of Rattus cause for species extinctions and attribute it to roughly macleari, a species of rat endemic to Christmas Island, 39% of extinctions of known cause in recent decades.20, has been attributed to the introduction of Rattus rattus, 21 In addition to immediately reducing the resources and the black rat, which carried fleas that hosted a nonnative territory available for each species, habitat destruction pathogenic trypanosome, to the island.30 This issue high- disrupts the geographical connections of species. It is of- lights the threat globalization poses to species diversity ten associated with an extinction debt, a process where by introducing harmful competitors, predators, or par- species that initially survive the change in their habi- asites. tat become extinct some time after, even if no further change occurs.22 This can arise via a variety of mecha- Humans are also responsible for increasing levels of envi- nisms, such as different survival rates at different points ronmental pollutants, such as chemicals and pesticides, in the lifecycle, increased threat from