Chapter one
1.0 Introduction
1.1 Background to the study
The earth’s vegetation is very rich in diverse phytobiota that sustains man and his livestock.
Man’s dependence on plants dates back to man’s origin. Of all the vegetations, tropical
rainforests have been reported to contain the greatest number of various types of plant species
(Nzekwe et al.,1993; Singh, 2004; Gurevitch et al., 2002). Singh (2004) reported that
tropical rainforests occupy about 8% of the earth’s surface. Of all the tropical rainforests,
those in the developing countries have been reported to be the reservoir of plant bioresources,
and contain about 60-90% of the total number of plants on earth (Isichei, 2005). Man depends
on plants for his diverse food requirements either directly or indirectly. Okafor (1983)
reported that man obtains food from plants in the form of grains, stem and root tubers, seeds,
nuts, fruits and leafy vegetables among others.
Numerous authors have reported that plants constitute the major sources of man’s industrial
raw material (Okafor, 1981; Okafor, 1983; Isichei, 2005; Okojie,1993). Apart from food and
industrial raw materials, several reports have revealed that man obtains herbal drugs, dyes,
spices and other numerous resources from plants for his well being as well as other socioeconomic
reasons ( Okafor, 1981; Sofowora,1982; Mendelson and Black, 1995; Okafor and
Ham, 1999; Anon, 2005). Despite the indispensable roles plants play in man’s socioeconomy,
reports have shown that the forests that habour the plants are being rapidly
depleted (Nzekwe et al.,1993). Depletion of the forests, particularly, tropical rainforests has
been globally associated with various factors of which increase in population and
advancement in technology are prominent.
Several ecologists have given insight on the rate of depletion of the world’s tropical
rainforest and its endangered status. Nzekwe et al.(1993) reported that about twenty million
hectares of land are lost annually in the world as a result of anthropogenic activities. Anyiam
(1995) reported that in the 1950’s, about 40% of the earth’s surface was occupied by the
tropical rainforests, and by 1975, the forested area was reduced to about 15%. Wilson (1992)
pointed out that progressive depletion of the tropical rainforests has reduced it to 10%. Many
environmentalists have shown that Africa alone has lost about 65% of her original rainforests,
while Central America and Asia have lost about 66% of theirs (Wilson, 1992; Nzekwe et
al.,1993; Mendelson and Black, 1995). Wilson (1992) pointed out that if the rate of the
depletion of the rainforests continues, it could result in their disappearance in about 25-30
years time.
Similar alarm was also raised by Sayer and Whitemore (1991) about the depletion of the
tropical rainforests. The authors pointed out that if the depletion of the tropical rainforests is
not put on check, most plant species as well as animals would be driven into extinction in
about 30 years time. The authors further pointed out that the disappearance of the tropical
rainforest would be a great global setback in the availability of biodiversity. According to
them, Nigeria is among the twelve nations whose deforestation rate accounts for about 80%
of the global total. With the recent climate change and its effects on the vegetation and the
ongoing deforestation,
1.0 Introduction
1.1 Background to the study
The earth’s vegetation is very rich in diverse phytobiota that sustains man and his livestock.
Man’s dependence on plants dates back to man’s origin. Of all the vegetations, tropical
rainforests have been reported to contain the greatest number of various types of plant species
(Nzekwe et al.,1993; Singh, 2004; Gurevitch et al., 2002). Singh (2004) reported that
tropical rainforests occupy about 8% of the earth’s surface. Of all the tropical rainforests,
those in the developing countries have been reported to be the reservoir of plant bioresources,
and contain about 60-90% of the total number of plants on earth (Isichei, 2005). Man depends
on plants for his diverse food requirements either directly or indirectly. Okafor (1983)
reported that man obtains food from plants in the form of grains, stem and root tubers, seeds,
nuts, fruits and leafy vegetables among others.
Numerous authors have reported that plants constitute the major sources of man’s industrial
raw material (Okafor, 1981; Okafor, 1983; Isichei, 2005; Okojie,1993). Apart from food and
industrial raw materials, several reports have revealed that man obtains herbal drugs, dyes,
spices and other numerous resources from plants for his well being as well as other socioeconomic
reasons ( Okafor, 1981; Sofowora,1982; Mendelson and Black, 1995; Okafor and
Ham, 1999; Anon, 2005). Despite the indispensable roles plants play in man’s socioeconomy,
reports have shown that the forests that habour the plants are being rapidly
depleted (Nzekwe et al.,1993). Depletion of the forests, particularly, tropical rainforests has
been globally associated with various factors of which increase in population and
advancement in technology are prominent.
Several ecologists have given insight on the rate of depletion of the world’s tropical
rainforest and its endangered status. Nzekwe et al.(1993) reported that about twenty million
hectares of land are lost annually in the world as a result of anthropogenic activities. Anyiam
(1995) reported that in the 1950’s, about 40% of the earth’s surface was occupied by the
tropical rainforests, and by 1975, the forested area was reduced to about 15%. Wilson (1992)
pointed out that progressive depletion of the tropical rainforests has reduced it to 10%. Many
environmentalists have shown that Africa alone has lost about 65% of her original rainforests,
while Central America and Asia have lost about 66% of theirs (Wilson, 1992; Nzekwe et
al.,1993; Mendelson and Black, 1995). Wilson (1992) pointed out that if the rate of the
depletion of the rainforests continues, it could result in their disappearance in about 25-30
years time.
Similar alarm was also raised by Sayer and Whitemore (1991) about the depletion of the
tropical rainforests. The authors pointed out that if the depletion of the tropical rainforests is
not put on check, most plant species as well as animals would be driven into extinction in
about 30 years time. The authors further pointed out that the disappearance of the tropical
rainforest would be a great global setback in the availability of biodiversity. According to
them, Nigeria is among the twelve nations whose deforestation rate accounts for about 80%
of the global total. With the recent climate change and its effects on the vegetation and the
ongoing deforestation,
