uniqueness. Although the exact ecological role or niche of each species in an ecosystem may be different from that of every other species, there is often considerable overlap or redundancy in the functional roles of species. For example, no other forest herb may fill the exact niche of a Canada mayflower, but there are other species that are also fixing carbon, providing a substrate for soil fungi, providing food for pollinating insects and fruit‐consuming small mammals, and so on. If these functional overlaps are sufficient, then it is likely that the ecosystem would not be profoundly changed by the disappearance of its Canada mayflower population. On the other hand, if a species is both very distinctive and has a keystone or dominant role, then its disappearance would most likely cause significant changes to an ecosystem. For example, the loss of elephants from African ecosystems can profoundly affect vegetation structure (Asner and Levick 2012) because no other species can deliver the ecological services, mainly disturbance, herbivory, and seed dispersal, that elephants do.
CASE STUDY 3.1 The Neem Tree
Wheat, corn, rice, potatoes – many species of plants have been profoundly important to the welfare of humanity. Indeed, some scholars have argued that one of the key defining events in western civilization was the hybridization, about 10,000 years ago in the Middle East, of two species to produce a form of wheat amenable to cultivation. From a historical perspective, at least one animal might rival these plants in its value: the horse, backbone of early transportation, exploration, and, too often, war. When we consider species in terms of the diversity of their instrumental values, not many species equal the neem tree, a member of the mahogany family from southern Asia (Fig. 3.14).
Figure 3.14 The neem tree provides an extraordinary array of useful products ranging from medicines to insect repellants, livestock fodder, and building material.
(StockImageFactory.com/Shutterstock)
The most remarkable thing about the neem is the myriad ways it is used as a health product. People use neem products to treat boils, burns, cholera, constipation, diabetes, heat rash, indigestion, malaria, measles, nausea, parasites, pimples, rheumatism, scorpion stings, sleeplessness, snake bites, stomach aches, syphilis, tumors, and ulcers, and they drink neem tea as a general tonic. They clean their teeth with neem twigs and neem‐derived toothpaste and make a disinfectant soap with the oil of neem seeds. Some research suggests that neem products may work as a spermicide and provide the basis for a birth‐control pill for men.
These marvelous features may account for the spiritual importance of neem as well. It is considered sacred by many Hindus, and its leaves are hung in the doors of a house and burnt as an incense to ward off evil spirits. Some Hindu holy men place neem twigs in their ears as a charm. The wood of the neem, attractive, strong, and durable, is one of few types used for carving idols. Returning to secular uses, neem wood is also used for fuel, furniture, and house building; neem foliage and seeds are used as livestock fodder; and neem seed oil is used as lamp fuel and to make lubricants and disinfectants. Neem trees grow well on marginal sites, making them appropriate for reforestation, and they produce a deep shade that is especially valued in hot climates. People place neem leaves in their cupboards, grain bins, beds, and books to repel insect pests. Various neem extracts are also effective as repellents and antifeedants for insects and nematodes that are agricultural pests.
The qualities of the neem are well known among millions of people in the Indian subcontinent, where it is often called the “village pharmacy,” and it has attracted attention beyond the borders of India as well as being evidenced in three volumes (Vietmeyer 1992; Schmutterer and Wilps 1995; Ferlow 2016) that provided the basis of this account.
Summary
There are many ways to define species, and decisions on what constitutes a species can have significant ramifications for conservation activities. It is generally desirable for conservationists to seek to maintain all distinguishable taxa, whether or not there is full agreement on definitions of “species,” because they represent significant genetic diversity. Approximately 1.3 million species have been described by scientists, but the actual number of species that exists is certainly much greater because there are large numbers of undescribed species. Although conservation biologists cannot hope to work with each species, it is useful to know the magnitude of what we might lose if environmental degradation continues.
One can argue that every species has intrinsic value; in other words, its importance is independent of its relationships with people and all other species. From this perspective, conservationists usually evaluate the importance of a species relative to how endangered it is. This is the basis for the lists of species jeopardized with extinction maintained by many organizations. Instrumental values, which are based on the usefulness of species, differ greatly among species. Many species have economic value because they provide food, medicine, materials, fuel, recreation, and various services for people. Species also have aesthetic, spiritual, scientific, and educational values that go beyond economics. They have ecological importance to many other species because of their roles in ecosystems, especially if they are dominant or keystone species. They can be of strategic value to conservationists by serving as flagship, umbrella, or indicator species. Some of these instrumental values are currently realized; many of them are potential values because they have not yet been expressed. Finally, species vary in their taxonomic uniqueness, and species that have no closely related species are generally considered more important than species with many close relatives.
FURTHER READING
For a classic account of how species diversity arises, how many species may exist, and related issues, see Wilson (2010). More detailed accounts are available in Huston (1994), Heywood and Watson (1995), and Scheffers et al. (2012). The World Conservation Union maintains www.iucnredlist.org, which lists and describes endangered species. For an overview of some of the instrumental values of species see Chivian and Bernstein 2008, and for thoughts on intrinsic value see McCord 2012. Also see species2000.org for a global effort to list all the world’s species, www.gbif.org, eol.org and www.unep‐wcmc.org for global biodiversity information and data repository sites, natureserve.org for information on species in the western hemisphere, and tolweb.org/tree for information on taxonomic relationships.
TOPICS FOR DISCUSSION
1 If you had a large budget to support global conservation biology research, say $200 million per year, what percentage of it would you allocate to: (a) estimating the number of species in existence; (b) surveying and classifying little‐known groups of organisms; and (c) studying species and ecosystems known to be threatened? Defend your budget. How would your budget change if your activities were confined to the continent you live on and the adjacent oceans?
2 Should a species' instrumental value be evaluated when deciding whether to place it on a list of endangered species that will be a priority for conservation efforts? Why or why not?
3 What approaches would you use to estimate a species’ potential instrumental value? Should potential values influence conservation decisions?
4 Should we seek to eradicate species such as the smallpox virus, or should we confine them to research laboratories where they cannot harm people?
