Lecture 10. Plant resource pools and systematics

Summary

Of the world’s estimated 270,000 plant species, some are global commodities, while others are important on a regional or local level. There are diverse ways of managing these botanical resources and estimating their economic value. Various economic, biological and social factors affect the sustainability and conservation of these resources. This lecture addresses how to characterize the world’s botanical diversity, using modern plant systematics and Bates’s concept of resource utilization pools. In later lectures we will address how to calculate the monetary and non-monetary value – and the threats to the diversity and sustainability – of botanical resources in each pool.

Ethnobiologists and economic botanists have devoted much effort to enumerating the many biological resources used by people around the world. Bates (1985), in an analysis of the number and importance of ethnobotanical and plant genetic resources, grouped all useful plants into a pyramid of primary, secondary and tertiary plant utilization pools. These three categories are based not only on the degree to which people and the world economy depend on individual species, but also the extent to which people have cultivated, domesticated and otherwise experimented with these plants. Further, the pools reflect three related historical trends in plant and animal use, including (1) the gradual substitution of hunting and gathering by agriculture and animal husbandry; (2) the domestication and spread of a few common types of staple crops and animals in various regions of the world, displacing numerous sources of food used locally; and (3) the reduction of the number of species used in agriculture, diet and trade over time.

Facts:

• There is a primary pool approximately 100 species that are the staple plants of the world. These are all cultivated and include the major domesticated crops that provide food, beverage, fiber, sugar, starch, oil, rubber and other products. The cultivation and genetic improvement of these plants are focused on providing large yields of a single commodity or raw material, produced and traded internationally. Ninety percent of the world’s food comes from 30 of these primary pool species, although approximately 7000 crop species are available for cultivation.

• The secondary pool includes some 1000 species that are important on a regional or national scale. They are often multiple-use plants and are usually cultivated, but are not necessarily domesticated. Some, such as timber trees, are harvested from non-cultivated lands.

• The tertiary pool is composed of an estimated 50,000 species - excluding some useful plants such as ornamentals and fuel sources - that serve the needs of people in subsistence economies. They are mostly managed or wild plants, although a few are sporadically cultivated. Many have multiple uses.

• Although not mentioned by Bates, there is a reserve pool of plants not currently used by people, but may prove to be valuable botanical resources in the future. Even if not directly used, these species play an important role in maintaining watersheds, soil quality and other aspects of the world environment that have an impact on agriculture and human welfare in general. If Bates’ estimates for the primary, secondary and tertiary pools are correct, this reserve includes approximately 220,000 of the estimated 270,000 plant species alive today.

Questions for discussion:

• Is the global botanical resource pool increasing or decreasing in diversity?
• What are the subsistence and commercial activities responsible for this increase or decrease in diversity?

Perspective for discussion:

"A convenient, though not absolute, way of summarizing the foregoing substitution, predictability and diversity/simplification themes and measuring the degree of human involvement with and dependence on individual species is in the characterization of primary, secondary, and tertiary species pools.

The primary pool is composed of the staple plants of civilization, not food plants alone, but all of which are of major importance, generally speaking, on an international basis. This pool is relatively small, consisting worldwide of perhaps 100 species. Of that number, but with some overlap in categories, about 25 are food plants; 5 or so, but with cotton overwhelmingly dominant, are fiber plants; 2 are sugar sources; perhaps 10 each yield starch and vegetable oils, 1 rubber, and 3 beverages; and so on through other categories. The plants now constituting the primary pool are cultivated plants, principally cultigens. In the context of our present culture and technology, they are not only the foundation of our agricultural establishment but of our civlization. From them, man draws the greatest percentage of his needs. In them, he invests and concentrates his economic, academic, technological, and other resources. For them, he stores germplasm and seeks new lands for cultivation.

The secondary pool augments and complements the primary pool, sometimes internationally, but more commonly on a regional or national basis. Categorically, it mirrors the primary pool, but categories often are not stringently defined and may be larger. For example, food plants of this pool not only provide regional staples but also a variety of fruits and vegetables that add richness to the human diet. The number of species that comprise this pool is probably fewer than 1,000. Most of the plants of this category are cultivated, some are cultigens. Others, especially those providing timber and forage, and even commodities, such as oils, may be harvested from the wild or from protected native stands.

The tertiary pool, composed of wild, protected, and even sporadically cultivated species, continues to provide a wealth of items to subsistence economies and remains the most important source of timber, timber-related products, and fuelwood. The number of species constituting this pool, exclusive of ornamentals and plants used for fuel, is unknown but may be as many as a fifth the size of the total number of seed plants, or some 50,000 species."

From Bates, D. 1985. Plant utilization: patterns and prospects.

References:

Bates, D. 1985. Plant utilization: patterns and prospects. Economic Botany 39:241-265.

Casas, A. and J. Caballero. 1996. Traditional management and morphological variation in Leucaena esculenta (Fabaceae: Mimosoideae) in the Mixtec region of Guerrero, Mexico. Economic Botany 50:167-181.

Clement, C.R. 1999. 1492 and the loss of Amazonian Crop Genetic Resources. I. The relation between domestication and human population decline. Economic Botany 53:188-202.

Clement, C.R. 1999. 1492 and the loss of Amazonian Crop Genetic Resources. II. Crop biogeography at contact. Economic Botany 53:203-216.

Diamond, J. 1998. Guns, Germs and Steel: A Short History of Everybody for the Last 13,000 Years. London, Vintage. Chapters 4 – 8.

Heiser, Jr. C.B. 1990[1973]. Seed to Civilization: The Story of Food. Cambridge, Harvard University Press.

Johns, T. 1990. With Bitter Herbs They Shall Eat It: Chemical Ecology and the Origins of Human Diet and Medicine. Tucson, University of Arizona Press.

Nabhan, G.P. 1989. Enduring Seeds: Native American Agriculture and Wild Plant Conservation. San Francisco, North Point Press.

Salick, J. 1992. Crop domestication and the evolutionary ecology of cocona (Solanum sessiliflorum Dunal). Evolutionary Biology 26: 247-285.

Sauer, C.O. 1975[1952]. Seeds, Spades, Hearths and Herds: The Domestication of Animals and Foodstuffs. Cambridge, The MIT Press.

Visual Aids:

Figure 1. The contribution of reserve, tertiary and secondary plant utilization pools to the maintenance of crop diversity at the primary level of the plant resource pyramid.

Use of wild plants and animals for food and medicine by farming communities

Sources: Pimbert, M. 1999. Sustaining the Multiple Functions of Agricultural Biodiversity. FAO background paper series for the Conference on the Multifunctional Character of Agriculture and Land, The Netherlands, September 1999. Citations: (1) Grivetti, 1979 (2) Hecht et al, 1988; (3) Zhaoqung and Ning, 1992; (4) Dei, 1989; (5) Oommacha and Masih, 1988; (6) Juma, 1989; (7) Wanjohi, 1987; (8) Okafor, 1989; (9) Cunningham, 1990a, b; (10) Harlan, 1989; (11) Ogle and Grivetti, 1985; (12) Somnasung et al, 1988; (13) Fowler and Mooney, 1990; (14) Scoones et al, 1992; (15) Wilson, 1990.

Exercises:

1. Complete the following table, providing definitions, examples, numbers of species, management, valuation and conservation issues for each resource pool.
2. Gather basic information on several useful plant species – consulting ethnobotanical literature or the Internet – and provide evidence for (a) what resource pool they belong to; and (b) whether they are gaining or losing importance in global and regional production.

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