Māris kļaviņŠ, azamat azizov, JĀnis zaļoksnis environment, pollution, development: the case of uzbekistan

Figure 9.5. 
Pesticide 
amounts in the 
countries with different 
development paths
Figure 9.6. 
Pesticides 
used in the countries 
with different 
development paths
Figure 9.7. 
Amounts of 
pesticide use in different 
countries of the world

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194 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
The negative effects of pesticide use on the soil ecosystems are 
related to the fact that these chemicals have an impact not only on 
pests, for whose destruction they are intended, but also on other 
components of the ecosystem. Moreover, many of the pesticides 
prove to be substances or a great chemical persistence and may 
accumulate in the ecological food chain: soil – plants – herbivores – 
carnivores. Pesticides do not remain on the field, where they have 
been  sprayed.  Air  currents  and  winds  easily  pick  up  the  volatile 
substances and carry them into the upper layers of atmo sphere and 
distribute them all over the planet’s surface. Thus, they end up in 
the places that are far away from intensive farming areas – ocean 
islands and the Arctic. The ability to accumulate in the ecological 
food chain makes the pesticides released into the environ ment 
potentially dangerous it even in very small quantities. Due to the 
characterstics described above, the pesticides account for the world’s 
most serious environ mental problems.
The impact of pesticides can be acute and chronic. In case of 
an acute impact, as a result of the pesticide exposure the extinction 
of the entire species or part of it when in contact with the toxic 
substance can be observed. In Europe, the intensive herbicide use in 
grain fields to combat weeds resulted in disappearence of flowering 
plants  such  as  cornflower,  corn  cockle,  the  forking  larkspur,  field 
poppies  and  other  –  the  species  so  characteristic  of  corn  fields  in 
the past have almost completely vanished in very large areas. 
Severe ecological consequences were brought by herbicides in the 
middle of the last century, during the Vietnam War. U.S. soldiers 
sprayed the herbicides from airplanes to achieve jungle defoliation – 
tree and shrub foliage thinning. For this purpose 2,4,5-T 
(2,4,5-trichlorophenylacetate) and 2,4-D (dichlorophenyl acetate) 
were used. These substances in high concentrations impact the cell 
layer at the leaf petiole base, and as a result the leaf is detached 
from the branch. Most commonly, after exposure to the herbicide 
the tree is able to renew its foliage. However, a particular sensitivity 
to these herbicides was manifested by mangrove woods growing in 
Vietnam’s low, swampy areas, and in these woods the prevalence of 
dominant shrub species declined catastrophically. 
It is important to note that in the course of 2,4,5-T production 
2,3,6,7-tetrachlorodibenzodioxine is created, which is generally 
contained by the herbicide in the form of admixture. Even in tiny 
concentrations  dioxins  cause  teratogenic  effects  in  animals  and 
humans – severe congenital malformations, and resulted in dramatic 
effects for many years after the Vietnam War. During 50s of the last 
century in the south-eastern states of the United States the combat 
was carried out to destroy the introduced red ants. In the course of 
three years, from aircrafts, 110 000 km
2
 were covered with granular 

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9. POLLUTION OF SOIL 
 195
heptachlor and dieldrin, in total spraying 1 km
2 
with 1.4 to 2.5 kg of 
insecticides. As a result, many passerine birds, skylarks and starlings 
as well as reptiles were killed; the number of insects living in the 
soil decreased by 40%, but the ants was not completely destroyed. 
Chronic exposure may result in disturbed reproductive capacity 
of the organisms, the birth rates are reduced, or mortality increases. 
If the individuals of a population become infertile, or unable to 
perform reproductive functions normally, the population is at a risk 
of extinction. Such chronic exposure usually becomes manifest, as 
different species of organisms accumulate pesticides in the ecological 
food chain. It turns out that plants can absorb small amounts of 
pesticides from the soil through the roots. Several studies have 
shown that further concentration of insecticides in the ecological 
food chain is largely dependent on the type of feeding characteristic 
to  species.  A  lower  insecticide  concentration  was  found  in  the 
organisms of herbivorous birds, the concentration in omnivorous 
species is higher, but the greatest concentration is observed in the 
organisms of the birds of prey.
One of the sources causing bird poisoning and death is the 
mercury-containing fungicides and grain mordants. These are 
used as pre-sowing treatment of seed to protect the seed from 
pests and the effects of microscopic fungi. Swedish researchers in 
1960 concluded that a decline in bird populations in the region is 
due to their chronic poisoning with fungicides. Mercury content in 
liver and kidneys of dead pigeons reached 8-45 mg/kg, in those of 
certain passerine grain-eating birds – 11-136 mg/kg, and in those 
of gallinaceous birds – 28-150 mg/kg. Through the ecological food 
chain the mercury entered birds of prey, in whose bodies it reached 
an average concentration of 100 mg/kg. 
The extensive use of DDT in agriculture is the main cause of the 
decline in populations of birds of prey in many regions of the world. 
Chronic poisoning with this pesticide its chemical transformation 
product DDE causes physiological changes in the bodies of birds, as a 
result the females become sterile, the start of the oviposition period is 
delayed, the number of laid eggs is reduced. In addition, the decrease 
in eggshell strength is observed and, consequently, there is an 
increase in destruction of juvenile birds already in embryonic stage.
Population  of  a  species  may  also  suffer  even  if  the  pesticide 
does  not  affect  it  directly,  i.e.,  as  a  result  of  indirect  exposure  to 
the toxicants. It is possible in cases where the particular species is 
trophically related to a species sensitive to the toxic effects. Decline 
or disappearance of food resources may prove to be critical for a 
given  species.  For  example,  the  disappearance  of  field  poppies  in 
large territories of Europe caused population decline of a number 
of  insect  species,  which  were  feeding  on  this  plant.  After  the  use 

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196 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
of herbicides the vegetation does not develop after harvest on the 
fields. This reduces the food base and hiding places for a number of 
animal species, such as grey partridges. Using the insecticide sevin 
to combat locusts in South Europe, it was found that the pesticide 
treated areas had 86% reduction in the number of birds. Given that 
birds were not hurt by sevin as a chemical, the only explanation was 
the extinction of food resources – insects.
The species which are tolerant to pesticide exposure can 
reproduce even if as a result of pesticide exposure their competitors 
or natural predators are killed. Very often it has been observed 
that,  as  a  result  of  pesticide  use  along  with  the  targets  –  harmful 
organisms  –  their  natural  enemies  are  also  destroyed.  Often  this 
is the reason for a new, even greater multiplication wave of the 
parasites  after  the  effect  of  pesticide  has  already  expired.  It  has 
been  proved  that  in  case  of  pesticide  use  the  worst  affected  are 
the populations of the pests’ natural enemies. They can even be 
completely destroyed locally. A similar situation was found regarding 
the cotton pest management in the United States and South America. 
Systematic use of pesticides totally destroyed the natural enemies of 
pests. As a result, the pesticide dose and frequency of treatment had 
to be constantly increased until a vicious circle was formed: the pest 
population growth required to increase the treatment with pesticides, 
but each new treatment led to new multiplying of parasites.
Over the last 10-15 years volume of pesticides and mineral ferti-
lizers usage in Uzbekistan reduced 3-4 folds. Despite the significant 
cut down in consumption of chemical compounds in agriculture, 
the problem of soil contamination with residual amount of toxic 
substances is not losing the actuality. Over the period since year 
1990 to 2006 a tendency of decrease of average level of irrigated soil 
contamination with residual DDT in Uzbekistan has been observed 
and the number of cases of exceedances in permissible limits in 
samples collected decreased from 39.2% to 21.1%. Increased level of 
soil contamination with residual DDT still persists in Andikansk and 
Fergansk regions and is 2.4-6.1 of limit values.