Conservation and Sustainable Use of the Biosphere - WBGU

Conservation and Sustainable Use of the Biosphere - WBGU

Agrobiodiversity: functions and threats under global change D 3.4


parative studies. Extensive studies have been carried

out solely on the state of ex-situ stocks of animal and

plant genetic resources, and even here only for the

main species (FAO, 1996b). To improve the characterization

of the status and thus the prognosis of loss

there should be a worldwide inventory and cataloguing

exercise as soon as possible (Section J 1.2).

Genetic diversity within crop species is distributed

regionally in very different ways. Since both generation

and preservation of this diversity depend on

human intervention, important political and economic

questions arise with regard to the equitable

distribution of burdens and tasks (Section I 3 and

Chapter J).

D 3.4.4

Agrobiodiversity under threat

Agriculture uses just a small portion of the entire

species spectrum in the form of planned biodiversity,

but over the 10,000 or so years of its existence has

brought forth an enormous diversity of varieties and

breeds within the species it has used.

There are a number of different reasons for the

decline in anthropogenic agrobiodiversity. The FAO

(1996b) cites population growth, wars, extreme

weather conditions (especially drought), pollution,

unsustainable agriculture, statutory regulations and

economic factors in particular. Hammer (1998)

determined that the main causes of loss of agricultural

species were overuse, disuse and neglect, mistakes

in determining species and displacement by

other species.

From this list we can derive the following issue

areas that have a direct influence on agrobiodiversity:

1. change in demand for agricultural produce,

2. agricultural management,

3. development of plant breeding technology,

4. agricultural and economic policy (impacting, in

turn, on the first three points).

Issue area 1: Change in demand for

agricultural produce

Agro-ecosystems are defined as systems that were

created to produce certain goods and services.

Demand for the products and a services of an agroecosystem

therefore has a crucial influence on the

shape and structure of the system.

Although in principle only relatively few species

were originally suited to agricultural use (Diamond,

1998), even these are far from universally used, certainly

not to any significant extent (Fig. D 3.4-2). One

main reason for that is the fact that many species provide

similar products, eg carbohydrates, fat, protein,

Box D 3.4-2

Genetic variability at the level of varieties in

selected regions

In a given region often only a very few varieties of a crop

species will be planted. The actually cultivated genetic

diversity within that species is then very low. Just a few

examples to illustrate that point:

• In 1983/84 on 67 per cent of the land under wheat in

Bangladesh and 30 per cent of the area under wheat

in India, just one variety (Sonalica) was planted.

• In 1972 and 1991 studies carried out in the United

States demonstrated that of the eight main cultivated

species fewer than nine varieties each were being

planted on 50–75 per cent of the acreage.

• A study in the Netherlands found that of the nine

main cultivated species just three varieties were

planted on 80–100 per cent of the acreage (FAO,


• In 1985 60 per cent of the acreage under winter wheat

in Germany was planted with five varieties that all

had the Capelle variety as a parent or grandparent

(Becker, 1993).

milk, meat, wool, bedding, fuel, etc. In most regions,

however, one species – often the one with the highest

yield in those circumstances – becomes the main supplier

of such product categories; so for example in a

given region in general one of either wheat, maize or

rice is planted as the main provider of carbohydrate

(FAO, 1996b).

New technological developments allow agricultural

products to be altered to such a degree in the

process of their preparation as foodstuffs that very

few basic raw materials are required. For example,

using biotechnological methods, it is possible to manufacture

isoglucose from starch. Currently, the food

industry in the USA is meeting a great deal of its

sugar needs from maize starch. This has led to a

strong decline in the importance of raw sugar imports

(Knerr, 1991).

Another approach tries to deliver differing product

qualities with a regionally well-adapted species.

So, for example, varying qualities of oil from oil seed

rape (Brassica napus L.) are produced in order to dispense

with having to plant other oil plants or import

oils. Transgenic rapeseed with high lauric acid levels

in the oil could take over from coconut and oil palms

in the future as the supplier of lauric acid (Sovero,

1996) and reduce demand from the industrialized


Varieties are also often not primarily cultivated

because they are most ecologically suited to the prevailing

conditions, but because they provide a certain

quality of product. With the increasing requirements

upon non-perishability, suitability for storage and

transportation, there has been a distinct impoverish-

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