Читать книгу Ecosystem Crises Interactions - Merrill Singer - Страница 42

Biodiversity “is changing across the world and this change is mostly negative” (Turak et al. 2017) from the standpoint of health across species (Butchart et al. 2010), a pattern known as bioadversity. A growing body of research, for example, indicates that among many species there are shifting habitat ranges, seasonal activities, life cycle events (e.g., the time of emergence of leaves and flowers or the arrival dates of migratory birds), predator–prey interactions, and migratory patterns (Forcada & Hoffman 2014; Zhang et al. 2014). Change in these and other features is not new. Since they appeared on the planet, plants and animals have reacted to environmental changes by adapting in various ways (e.g., changing color, body shape, behavior), migrating to new areas with different conditions, or, if unable to adapt successfully, going extinct. Which of these possibilities lie ahead for the current inhabitants of Earth, including ourselves? According to Nogués‐Bravo et al. (2018), “How individual species and entire ecosystems will respond to future climate change are among the most pressing questions facing ecologists.” But the issue is not just climate change—the same applies to species and entire ecosystem responses to other adverse anthropogenic environmental modifications.

With regard to human health, maintaining biodiversity is of vital importance. Human medicines often are first discovered in wild‐dwelling species. So too are various pathogens and disease vectors, which can only be brought under control by studying their behaviors and habitats. As Chivian (1997, p. 8) maintains:

The study of species and biodiversity may be the best means we have for recognizing future dangers to human health from global environmental degradation … [W]e must focus much greater attention on biodiversity loss, which looms as a slowly evolving, potential medical emergency of unprecedented proportions, still largely unappreciated by policymakers and the public.

A species of considerable interest with regard to medicine development is the great white shark (Carcharodon carcharias), an animal that usually is far more terrifying in our imaginations than it is in reality. Found as a top predator in the coastal surface waters of all the major oceans, great whites face multiple anthropogenic challenges (e.g., accidental deaths on fishing longlines, poaching for the shark fin soup market, sport fishing for shark jaw trophies, ocean pollution). The scale of these threats has led the IUCN to list them as a vulnerable species and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) as an Appendix II species (i.e., a species for which trade must be controlled in order to avoid human utilization that is incompatible with its survival). Medical interest in great whites stems from the fact that they are known to be super‐healers. During their long evolutionary history, they have developed a genetic tool‐kit that enhances several key processes involved in wound healing. These include sequences of DNA that code for rapid damage response, including amplified blood‐clotting agents and scaffolding proteins that serve as the foundation for new tissue. Not only do great whites have uniquely adapted versions of these genes, but it appears that they have them in greater supply than other species, including us. Moreover, in theory, sharks and other large‐bodied, long‐lived animals with many more body cells than humans should have a greater chance of developing oncogenic mutations. Great whites, however, do not have a higher incidence of cancer than humans, and this may be because of clusters of genes that protect the integrity of their genetic code itself, a trait known in biology as genome stability. “Understanding how these genes might be inoculating these animals from cancer could be a huge benefit to humans,” according to Michael Stanhope (quoted in Molenti 2019), an evolutionary biologist at Cornell University who co‐led a project to map the great white genome (Marra et al. 2019).

Because “global biological diversity is declining in the face of numerous pressures” (Wetzel et al. 2017, p. 78), and this loss has grave implications, since the early 1970s biodiversity has emerged as a critical and heated scientific and political issue. In the case of sharks, their potential relevance to human health goes beyond the issue of cancer and includes their ability to heal quickly from wounds and resist infections. By sequencing the sharks’ genome, researchers are trying to identify which genes contribute to these abilities and translate this finding into advances in wound‐healing human medicines. Already, a skin‐graft device called the Integra Omnigraft Dermal Regeneration Matrix (Omnigraft) has been approved by the U.S. Food and Drug Administration (FDA 2016). This material, which uses a combination of silicone, cow collagen, and shark cartilage, is used to help heal certain life‐threatening burns and diabetic foot ulcers. The medical potential of the shark genome also extends to a possible new way of treating pulmonary fibrosis, a lung disease that occurs when tissue becomes damaged and scarred, making it difficult for the lungs to work properly and causing progressive shortness of breath. A new drug called AD‐114, which mimics shark antibodies, is being developing in Australia. It belongs to a class of therapies called i‐bodies, which are proteins that combine the features of small molecules and antibodies. In animal testing, AD‐114 has been found to only bind with scarred lung cells while ignoring healthy lung tissue (Pulmonary Fibrosis News 2016).

At The Hague in 2002, the U.N. member states that signed on to the Convention on Biological Diversity agreed to a series of goals aimed at significantly reducing the rate of loss of animal and plant populations at the global, national, and regional levels—goals that have not been achieved. Blocking achievement are multiple threats to biodiversity (European Commission 2004), including:

 Unceasing expansion of industrial production, including many new chemicals,

 Promotion of hyper‐consumerism.

 Production of toxic waste and its release into the environment.

 Global increase in vehicular mobility.

 Stratospheric ozone depletion.

 Human population growth, leading to increasing demands for living space, food, and other resources. (The global human population has grown from approximately 1.65 billion in 1900 to an estimated 6.3 billion today, and is increasing by over 75 million a year. In 40 years, the United Nations predicts a world population of 9 billion).

 Urban expansion and commercial agriculture and forestry encroachments on habitats.

 Extension of roads, rail lines, airports, and electricity networks that fragment habitats and frighten away some species.

 Overexploitation of natural resources, including excessive hunting, collecting, and trade in species and parts of species.

 Pollution and its adverse effects on the health of animals and plants.

 Environmental disasters, such as oil spills that devastate marine and coastal fauna and flora.

 Climate change, which impacts ecosystems on the land and in the seas, causes sea level rise, enhances the intensity and frequency of wild fires, contributes to species decline and extinction, and significantly impacts health.

 Invasion of alien species, often introduced intentionally or unintentionally by humans, that thrive and overwhelm endemic species.

 Overfishing, which is depleting global fish stocks in lakes and oceans.

Not only does this wide array of environmentally adverse factors threaten biodiversity, the loss of which is a direct threat to health, but it also creates the conditions for co‐occurring and interacting ecocrises. As Noyes & Lema (2015) observe:

a large percentage of terrestrial and aquatic species are facing elevated risk of extinction with climate change acting as a major driving force that is worsened by interactions with other stressors including habitat fragmentation and modification, over‐exploitation and harvesting, eutrophication, invading species, infectious disease, and chemical pollution.

Another expression of ecocrises interaction is seen in the case of honeybees, which play a critical role in human food production. Research indicates that fruit, vegetable, and seed/nut production for 87 of the leading global food crops is dependent upon animal pollinators like bees (Klein et al. 2007). Historically, beehives in North America endured a die‐off rate of about 15 percent in the period between October and April because of the cold temperatures and lack of winter forage. Rates of loss, however, have almost doubled to 28 percent since the early 2000s as a result of the combined and interacting effects of stress, pests, diseases, and pesticide exposure (Goodrich 2017). In fact, in 2014, the United Nations reported that 40 percent of the plant pollinator species that are key to the world’s food supply are facing extinction. A member of the team that produced this assessment, Berry Brosi, assistant professor of environmental sciences and bee researcher at Emory University in Atlanta, stated: “If pollinator declines continue at this rate it will have serious implications not just for human food security and economics but also for biodiversity and the health of ecosystems in general … When we lose even one pollinator species from an ecosystem, it can degrade the functioning of the system overall … Studies have shown this relationship between biodiversity of pollinators and both agricultural productivity and plant reproduction in wild ecosystems … Nutritionally, the pollinator declines will likely have the biggest impact on the poorest people of the world” (quoted in Clark‐Emory 2016). Beyond nutritional issues, pollinators are needed for crops that are the source of biofuels (e.g., canola and palm oils), fibers (e.g., cotton and linen), forage for livestock, and construction materials like wood.