Bioprospecting, Sustainable Use and Maintenance of Biodiversity

Bioprospecting, Sustainable Use and Maintenance of Biodiversity

Paper presented at:

International Conference of Medicinal Plants, Traditional Medicines &
Local Communities in Africa: Challenges & Opportunities of the New
Millenium Nairobi, Kenya 16-19 May 2000

By:

Cathrine Amundsen1, Shivcharn S. Dhillion1,2 and Magnus Eriksen1

1Dept. of Biology and Nature Conservation, Agricultural Univ. of Norway,
pb 5014, Ås, N-1432, Norway ;
2Centre for Development and the Environment, Univ. of Oslo, pb 1116,
Blindern N-0317 Oslo, Norway.

Introduction
Medicinal plants, factories of unique chemicals and potential novel
pharmaceutical products, are targeted by many international parties,
often with questionable regard for environmental repercussions of
extracting from the wild, needs of local users, and the requirements for
the maintenance of biodiversity and ecosystems. Today there are few
regulations and policies developed by nations to protect and regulate
access to biodiversity. Of much concern to biologists has been the
question of the degree to which species can be exploited before they
become extinct, and changes that result in the system due to
exploitation. More specifically, to what extent does bioprospecting
constitute a sustainable activity.

This paper explores collection methods for species by bioprospectors,
characteristics of species vulnerable to harvesting, and the
requirements for the conservation of species which are harvested. In
order to illustrate plant characteristics vulnerable to collection, mode
and reason for collection, and conservation measures applied, we
selected medicinal plants on the basis of their known extensive use in
bioprospecting. We bring into light the scarcity of data on the species
biology of species collected either for drug discovery or
phytomedicines.

Which species to pick?
The choice of species may be based on a number of selection criteria
namely that: (1) the collection includes plants that provide a high
taxonomic diversity and novelty to the collection thus potentially
providing high diversity of types and classes of biochemical structures;
(2) the collection of plants is based on knowledge of traditional
medicinal uses; (3) the collections consists of plant families or genera
shown to be rich in active compounds; (4) ecological footprints based on
the observed relationships between plants, insects and other animals are
known; and (5) random collections.

Does collection impact plants and nature?
Common assumptions, many unsubstantiated, made on the harvesting of
entire or parts of species are, that: ‘these products can be harvested
sustainably with little or no negative effects on the forest resource
base’ (deBeer 1993); ‘non-timber products can usually be harvested with
little or no disturbance to soil or timber tree (or other woody species)
regeneration’ (Panayotou 1993); the collection/harvesting of different
plant parts has the same impact on the selected species; that species do
not have any specific habitat requirements different from that of most
other species; and the collection of one species does not impact another
species.

Life-form, growth and reproduction
The comparison (Table 1) shows that of the 12 selected scarce or
endangered medicinal plant species, 8 were in the category tree/shrub,
while 4 were herbs (1 annual/3 perennials). This is in consistence with
previous studies, where woody species are known to represent the most
vulnerable life-form, due to long maturity time, a low ratio of
production to biomass and specialised habitat requirements among others
(Cunningham 1991; Begon et al. 1996; Dhillion and Amundsen 2000).

The perennial herb Himalayan mayapple (Podophyllum hexandrum) listed in
CITES Appendix II (Table 1), is assumed to be one of the nine most
threatened exploited medicinal plants in trade (CITES 1994; Leaman and
Schippmann 1998). The harvesting of its roots probably deters vegetative
reproduction, which impacts regeneration and may be the reason for
population loss. The harvesting of the rosy periwinkle also consists of
uprooting, but this herb is not endangered per se (Sheldon et al. 1997).
Differences between these two species are their habitat requirements,
which for the mayapple is much more specialised than for the periwinkle,
and their life-form, the first being perennial and the latter annual
(Table 1). Both species have large scale demands, where large amounts of
plant material are needed to produce anti-cancer medicines . When it
comes to the other herbs, American ginseng (Panax quinquefolius) and
ipecac (Cephalis ipecacuanha) (Table 1), the harvesting of these
perennials also includes the extraction of the roots, often the whole
plant. The herbs in this comparison have also shown to be similar to
woody species, which could explain their vulnerability (long maturity
time, specific habitat requirements, 3/4: perennial life-form). The
harvesting of large quantities of whole plants or perennial roots by
NCI, Bristol Myers and other pharmaceutical companies, put a strong
pressure on wild populations, and is the main reason to the local/global
scarcity of these herbs.

The type of plant part harvested affects the maintenance of the
populations (Table 1; Cunningham 1991, 1993; Hall and Bawa 1993;
Salafsky et al. 1993; Peters 1994, 1997; Shankar et al. 1996; Sheldon et
al. 1997). It seems obvious that the harvesting of whole plants, bark,
roots or harvesting of any other part that decreases the survival of the
individual, and thereby its population, has a larger negative effect
than the harvesting of renewable parts such as fruits, seeds, leaves or
flowers; though bark can be renewable for some species (Prunus africana,
Cunningham 1991). The secondary compounds are often concentrated in the
roots, barks, and rhizomes (Table 1).

The removal of renewable parts like leaves can also lead to scarcity,
for example in the cases of Pilocarpus spp. and the chonodendron vine
(Chondodendron tomentosum) (Table 1). There are also other examples of
unsustainable harvesting of leaves (Hersch-Martínez 1997)--but as such
these are few, probably because the most common harvested medicinal
plant parts are roots or bark (Cunningham 1991). In many places whole
trees are felled to ease the collection of for instance fruits
(Cunningham 1993; Peters 1997).

Habitat requirements, distribution and abundance
Two-thirds (8 out of 12) of the endangered plants have specific habitat
requirements (Table 1). Studies by Cunningham (1991; 1993) on
commercially exploited medicinal plants in South Africa, further support
that species with specific habitat requirements are more vulnerable to
extraction (see also studies in Thailand, Dhillion and Ampornpan 2000).
In general, rarity makes a species more susceptible (Meffe and Carroll
1996; see discussions in Peters 1997; Boot and Gullison 1995; Hall and
Bawa 1993; Dhillion and Amundsen 2000)

Intensity of harvesting and conservation
The intensity of the harvesting, measured in quantity and frequency,
decides whether the harvesting is sustainable or not. A large-scale
demand favours a high intensity of harvesting. Sporadic or periodic
collections may have less impact but this also depends upon other
factors, as for instance harvest methods as time or location of
harvesting. The knowledge traditional communities possess about
sustainable harvest methods, ecology, biological requirements and
characteristics of medicinal plant species, can be vital information for
conservation (Gadgil et al. 1993; King 1994; Heywood and Watson 1995;
Balick and Cox 1996; Alexiades and Lacaze 1996; Carlson et al. 1997).

Alternative strategies to ease the pressure on wild populations or
increase supply of the medicinal compounds have been cultivation,
synthesising, enrichment planting or breeding for larger yields (Table
1). Species with special habitat requirements, slow growth or long
maturation time are in most cases too difficult to cultivate. Secondary
metabolites from plants may consist of complex molecules, developed in
the plant over decades. This makes the process of synthesising a medical
compound complicated, time-consuming, costly and, sometimes, impossible.
Only three of the selected species’ compounds are artificially produced
(Table 1), and one of these is still too expensive for commercial
production. However, current collections of 6 of the 12 selected species
in Table 1 employ alternative strategies that exceed wild extraction of
the plant--activities like cultivation and synthetic substitutes. If the
alternative strategies reduce the possibility of extinction of a
species, then the selected plants in Table 1 would probably not have
shown the observed pattern of population loss. Cultivation is in many
cases necessary, as supply from wild sources is limited, especially for
highly demanded species.

All the species (Table 1) had a large-scale demand prior to the
reduction of the populations. Without legislation or management of the
target species, excessive demand can lead to over-harvesting (Boot and
Gullison 1995; Sheldon et al. 1997; Hersch-Martínez 1997; Leaman and
Schippmann 1998; Cunningham 1991; 1993). The histories of species that
have been exploited so far point to the fact that a medicinal plant
species needs to become scarce before alternative supplies are developed
(Cunningham 1993; Sheldon et al. 1997).

It is also evident from the literature that the studies of species for
bioprospecting and conservation have rarely discussed species
biology/ecology and requirements for conservation (Dhillion and Amundsen
2000; Dhillion and Ampornpan 2000), even when the subject of the
publication has been to explore whether bioprospecting, conservation and
biodiversity management are compatible (see discussions in Sheldon et
al. 1997; Balick et al. 1996).

Intraspecific processes as a result of harvesting, and impacts on
tropical forests
Loss of biodiversity or changes in intra- or interspecific processes,
result in alteration of a community’s trophic levels, in addition to
loss of the functions that a community rich in diversity provides. The
consequence of loss of species or reduction in population size due to
isolation and loss of dispersal between remnant populations, can result
in inbreeding, genetic drift, loss of genetic variation or other genetic
changes, reduction in the vigour of harvested plants, decreased rate of
seedling establishment of harvested species, potential disruption of
local animal populations (dependent on the resources), and nutrient loss
from harvested material. A decline in recruitment appears when
harvesting is concentrated on reproductive adults or plant parts. A
level beyond the minimum viable population (MVP), may lead to loss in
genetic variation, and risks of extinction by demographic or stochastic
fluctuations (Newman 1993; Begon et al. 1996; Meffe and Carroll 1996;
Forman 1997). Harvesting can also affect the genetic composition of a
population, and change the size or quality of the plants or plant parts,
due to selective collections of ‘best yielding’ individuals.

Conclusion
Factors limiting the sustainability of harvesting medicinal plant
species are, among others: life-form, growth and reproduction
characteristics, plant-part harvested, habitat requirements,
distribution, abundance, and harvest intensity (see Table 1).
Alternative supply sources such as cultivation, synthetic substitutes,
or managing to increase populations, production or reproduction, have
the potential to reduce over-harvesting of species, but have largely
been employed for species that are already over-exploited. The
considerable investment in setting up conservation programmes and
conducting early studies of potentially important plants deters
financial input into conservation at large by bioprospecting
enterprises.

All the species explored here had a large scale demand prior to the
reduction of the populations. Without legislation or management of the
target species, excessive demand can lead to over-harvesting. The
histories of species that have been exploited so far point to the fact
that a medicinal plant species needs to become scarce before alternative
supplies are developed. It is also evident from literature that the
studies of species for bioprospecting and conservation, have rarely
discussed species biology/ecology and requirements for conservation.
Harvesting of natural populations in tropical forests has implications,
not only on the population level, but also on nutrient balance and
interspecific processes, and may result in irreversible changes in
community structure and functions.

Local communities possess useful traditional knowledge about these
complex systems, and should be better represented in discussions about
the sustainability of harvesting medicinal plant species. The lack of
recognition of local knowledge and skills in the management of species
extraction is a serious issue that needs attention with regard to
developing tools for conservation and management of diversity.

From all points of view, an incredible chemical laboratory still
practically untouched by scientific investigation for new therapeutic
agents is awaiting attention, and services are still far from being
determined. Indeed, the CBD calls for mandates that would maintain the
capacity of ecosystems to provide goods for current and future
generations. Biodiversity conservation and management must acknowledge
the importance of diversity and complexity, and anything short of this,
especially if only commodity based, would be short-sighted and not
likely to be sustained in the long term. It is best that we start
seriously interjecting sustainable use policies gained from ecological
studies of species and their habitats into all known and potential uses
of wildland resources. This, in the past and at present, is largely
non-existent.
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