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

Figure 4.11. 
Food web. 
Species that act at 
different levels of the 
food chain make the 
nodes of the food web, 
whereas species that 
consume just one type 
of food are linked to the 
web with a single link.
Herbivores
Green 
plants
Primary predators
Secondary predators
Figure 4.10. 
Ecological 
pyramid of numbers. 
Energy deficit and losses 
in the trophic food chain 
causes the situation 
when usually within 
an ecosystem there 
are more plants than 
herbivores and more 
prey than predators.

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4. HUMANS AND THE ENVIRONMENT
 55
Ecosystems at different levels of hierarchy are not isolated from 
one another; rather, they are interconnected in innumerable ways. 
For this reason, processes taking place in a system at a lower level 
affect both the neighbouring systems at the same level and all the 
ecosystems at higher levels in the ecosystem hierarchy. Thus, the 
number of migratory birds of a particular species, for example, 
the Black Stork, in some regions of Latvia depends on the survival 
success of this species in Africa.
The  Amazonian  rain forest  deforestation  causes  not  just  local 
climate changes; it also affects climate in the entire region of the 
Amazon Basin, South America and the Pacific Ocean, because the 
rain forest ecosystems, by means of intensive evaporation of water 
and  release  of  specific  substances  into  the  atmo sphere,  determine 
the height of rain cloud formation above the region. Ultimately, 
these changes affect the global climate as well. Admittedly, today’s 
knowledge on causal relationships in ecosystems is still incomplete. 
Theoretically it is possible that minor changes in one element of 
the  system  might  cause  significant  changes  in  the  whole  system. 
This  principle  is  metaphorically  denoted  as  ‘the  butterfly  effect’, 
and it also applies to causal relations in ecosystems, as expressed 
by the saying that the flap of a butterfly’s wings in the rain forest 
of  South  America  can  set  off  a  storm  in  Europe.  A  small  increase 
in the concentration of phosphorus-nitrogen compounds in a lake 
under favourable water temperature may cause an avalanche-like 
multiplication of algae and cyanobacteria (blue-green algae) that has 
a substantial effect on the whole ecosystem of the lake.
The hierarchic structure of ecosystems spatially manifests 
itself as the diversity of biotopes within a single ecosystem. A large 
diversity of biotopes is characteristic of natural landscape eco systems, 
where  all  kinds  of  ecosystems  alternate:  different  forest  types,  dry 
and wet meadows, peat bogs and marshlands, dunes, lakes. Landscape 
ecosystems with a low diversity of biotopes, in turn, in many cases 
are human-made: large tracts of human-planted forest, agricultural 
fields and pastures.
Species communities or biological communities represent the 
living components of the ecosystem. Biological communities consist 
of bacteria, fungi, plants and animals. These organisms depend on 
environ mental conditions (temperature, moisture, soil fertility), 
at the same time transforming these conditions themselves. For 
example, plants with roots and litter as well as animals with digging 
and excrements transform non-living rocks into soil. Earthworms 
play an outstanding role in this process. The famous British natural 
scientist Charles Darwin once compared them with a farmer’s 
plough because there are hundreds of earthworms per square meter 
of a field, and they continually feed on the soil, so that almost all 

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56 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
of the field’s topsoil passes through their digestive tracts within the 
period of one year. Earthworm castings are called coprolites, and 
they are chemically stable structural elements of the soil. In fact, 
they make the soil fertile by becoming the activity centres of the 
microbiological processes taking place in the soil.
A  characteristic  feature  of  a  biological  commu nity  is  species 
diversity measured by the number of species within the community. 
The highest species diversity is found in the ecosystems of tropical 
rain forests and coral reefs. For example, the entomologist Terry 
Erwin  has  discovered  that  an  average  of  1200  species  of  beetles 
inhabit the foliage of one species of tree in the Panamanian rain-
forest. Of course, the species diversity is much lower in the forest 
ecosystems of the northern and temperate zones, where the environ-
mental conditions are more severe. For example, in coniferous 
forests, the number of species can be easily counted on the fingers 
of one’s hand. Nevertheless, tens of different species of small arthro-
pods and worms live in the forest soil.
Ecosystems constantly change and develop. Biological commu-
nities transform into different ones, with a different composition of 
species. This development process of ecosystems is called ecological 
succession.  A  telling  example  of  ecological  succession  is  a  field 
overgrown with weeds and grass, transforming into a meadow; then, 
the meadow is overgrown with shrubs; and, finally, the shrubbery 
transforms into a forest (Figure 4.12).
Time period
Field 
Meadow  Shrubbery  Low deciduous forest 
Spruce forest
Ecological  successions  can  be  of  different  durations:  from 
relatively short-term to very long. There can be short micro-
successions that run for about a few weeks. In contrast, a gradual 
overgrowing of a lake and its transformation into a swamp may 
take thousands of years (Figure 4.13). The remains of aquatic plants 
and animals gradually settle on the lake’s bottom; consequently, it