LITMIR.BIZ

Скачать книгу

and sowing, or the risk of soil erosion.

      Second, wild species may be a source of new domesticates in the future. Domestication is almost as old as humanity, and it is still practiced (Meyer et al. 2012). To take two examples, salt‐tolerant plants may be domesticated to use on farmlands degraded by salinization (Rozema et al. 2013) and some of the nearly 2000 species of insects that people consume for food could be prime candidates for domestication (van Huis et al. 2013). Some of the food items that we associate with wild species are already produced primarily using captive populations; for example, most of the venison sold in markets comes from deer farms and most of the salmon and shrimp we eat are raised through aquaculture.

Third, wild plant and animal populations are still major food sources for people (Bharucha and Pretty 2010) (Fig 3.5). In particular, many rural people rely heavily on wild plants and animals (often called bushmeat) for food. It is easy to attribute this practice to the poverty that pervades much of the world. However, people clearly do not consume wild species just out of necessity. Indeed, wild food typically commands a better price than domestic equivalents. For example, in Ghana many wild species, especially grasscutter rats and brush‐tailed porcupines, sell for much more than chicken, pork, or beef (Cowlishaw et al. 2005) and furthermore Ghanaians living abroad will pay extraordinary prices to enjoy wild food from home: for example, they may pay 17–25 times more in New York City than they would pay in Ghana (Brashares et al. 2011). Hunters in the United States may spend the equivalent of hundreds of dollars per kilogram of duck or deer meat once all their investment in equipment, travel, licenses, and lost work is considered, but that misses the point of why they hunt. Of course, game birds and mammals are not the whole story; most of the fish and shellfish (more correctly mollusks and crustaceans) sold in the world – whether dipped from a bucket on the streets of Lagos or wrapped in plastic at a London supermarket – come from wild populations. These issues are particularly important for conservation biologists because: (1) wild populations are often overexploited (Chapter 9, “Overexploitation”); (2) conserving populations requires regulating harvests (Chapter 13, “Managing Populations”); (3) people often pay far more for these species than may seem “rational” and thereby drive exploitation to extreme levels; and (4) maintaining biodiversity requires special consideration for the well‐being of rural people because they share most of the habitat of wild plant and animal populations (Chapters 15, 16, and 17, “Social Factors,” “Economics,” and “Politics and Action”).

Figure 3.5 Although most of our food comes from domestic species, a wide variety of wild species are consumed ranging from the predictable, such as fruits [top], to the rather unusual, such as fruit bat soup in Guam [bottom].

      (Malcolm L. Hunter Jr., author) [top]; Courtesy of Merlin D. Tuttle/Bat Conservation International [bottom])

       Medicine

      There was a time when essentially all of our medicines, like all of our foods, came directly from wild organisms. Traditional medicines remain a conspicuous and valuable legacy of this past. This is especially true in developing countries where most of the world’s population resides and where much of the population may still depend on herb markets and herbalists as the primary source of medicine. It is also true in industrialized countries where herbal medicines are worth billions of dollars per year (Fabricant and Farnsworth 2001). A less obvious legacy persists in modern pharmaceuticals, about half of which include chemicals directly obtained from organisms or originally isolated and identified in an organism and then later synthesized by chemists (David et al. 2015). If you include non‐active ingredients the proportion is larger. For example, next time you are at a pharmacy read the ingredients list for the widely used hemorrhoid treatment “Preparation H”; you will find five diverse species represented as shark liver oil, beeswax, corn oil, sheep lanolin, and thyme oil. It is nearly impossible to attach a monetary figure to all of these values, but it is almost certainly in the hundreds of billions of dollars per year (Principe 1996; Kumar 2004).

Plants are a primary source of medicinal chemicals, largely because they have developed a wide diversity of complex organic chemicals (often known as secondary compounds) for deterring plant‐eating animals and other functions. One of the earliest examples is particularly poignant. Silphion was a plant in the carrot family from north Africa that became a major trade commodity in the Greek and Roman empires, primarily because of its efficacy as a human contraceptive (Fig. 3.6). Attempts to domesticate it failed and overexploitation of the wild population continued until it became so rare that it was worth more than its weight in silver. As with most extinctions it is difficult to determine the date, but by 77 CE when Pliny the Elder wrote his natural history, it had not been seen for many years (Parejko 2003).

Figure 3.6 Silphion was a plant of such great commercial value that it was depicted on Greek coins. However, its use (chiefly as a contraceptive) was short‐lived because it was apparently overharvested into extinction roughly 2000 years ago.

      (CNG Coins/Wikimedia Commons/CC BY‐SA 3.0)

Despite the advances of modern pharmacology, chemicals obtained or identified from nature remain very important (Cragg and Newman 2013). For example, in the Pacific Northwest of the United States the Pacific yew was transformed from a “trash tree” with no value as timber into an important medicinal plant when it was discovered to contain taxol, a chemical that has proven very effective in the treatment of ovarian cancer and breast cancer (Miller et al. 2008). Another example comes from the mountains of Ecuador where a rare shrub, Diplostephium rhododendroides, is the source of chemicals with great promise in the treatment of hepatitis C and diabetes (Ibrahim et al. 2013). Surveys for medically important plants have long been expedited by consulting with local people about their use of local plants (although less often sharing the commercial benefits of doing so); indeed there is a whole journal, the Journal of Ethnopharmacology, devoted to the topic, along with various journals that cover ethnobotany.

      Medicines derived from microorganisms include penicillin, tetracycline, and most other antibiotics, as well as a variety of vaccines, hormones, and antibodies (Cragg and Newman 2013). Better understanding of the role of the microbiome that occupies the bodies of larger organisms is likely to have profound implications for the practice of medicine, for people, domestic species, and those wild species that demand our attention (Qin et al. 2010; Huttenhower et al. 2012; Redford et al. 2012). An intriguing study from Finland found that young people living in diverse settings (as measured by the diversity of plant species and different types of land use) were less likely to suffer from allergies and this was tied to the diversity and abundance of beneficial bacteria found on their skins (Hanski et al. 2012).

Although animals are the source of some medicines – for example, chemicals used to prevent blood clots have been isolated from the saliva of two blood‐sucking animals, leeches and vampire bats – they are generally more widely used in medical science as biological systems to be investigated for insights. The role of mice, rats, and primates as surrogates for people in medical research is well known, but animals’ contribution to medical science goes far beyond this. For example, research on the metabolism

Скачать книгу