150
tant areas making soil unproductive and destroying pastures. Once thriving fishing produced
40,000–50,000 tonnes of fish each year for the tin
factory on the coast of the lake. Nowadays fish
recovery is reduced to 1000 tonnes per year and
60,000 fishermen lost their job. Life has been
almost completely perished from the lake, a real
ecological catastrophe can be witnessed making
even the economy of the surrounding countries
suffer. In 1995 Kazakhstan, Kyrgyzstan,
Tajikistan, Turkmenistan and Uzbekistan agreed
to save the remnants of Aral Sea. In 1997 UNEP
(International Fund for Saving the Aral Sea) and
later the World Bank supported financially the
works. A rehabilitation plan called INTAS Project
was prepared by 2006 stating the changes
required in the complete water system of the lake.
Regarding the plans the Kokaral Dam has
been realised with 86 million dollars of World
Bank support improving the water supply of the
remaining northern part of the Aral Sea as Syr
Darya supplies enough water for the rehabilitation of the North Aral Sea. Water level was raised
at a relatively rapid rate and the salt content of
North Aral Sea increased to 8–13‰ by 2018, i.e.
reaching the level of the 1960s. It seems likely
that the complete loss of the large lake can be
hindered; however, retrieving the original conditions (typical for the 1960s) is highly unlikely.
Warming climate threatens the glaciers supplying
Amu Darya and Syr Darya thus probably the
water supply of the Aral Sea will decrease.
Numerous lakes have similar problems like
the Aral Sea affecting of course people living on
their coast and in their catchment area.
Occasionally natural and social reasons together
threaten the water system of a large lake. An
example for this is Lake Chad in Africa (Coe and
Foley 2001) that is located in somewhat better
climatic conditions: although annual precipitation is only 300 mm in its northern part but in the
south annual precipitation exceeds 650 mm.
These average values hide extremely variable,
prolonged dry and wet periods. There are several
countries in the drainage basin of the lake.
Nigeria, Chad and Cameroon initiated irrigation
programmes in the 1970s in order to, among others, achieve adequate crop yield in a long dry
period. Especially the plans of Nigeria were
ambitious: 67,000 ha were planned to be irrigated
in the catchment area of the lake. The water system of the lake was further strained by a series of
settlements built on its coast using its water. The
result resembles the Aral Sea: rapidly retreating
water surface as the depth of the lake was small.
Open water disappeared by the 1980s as it was
covered by aquatic plants. Worryingly many nonnative species appear among the plants. Irrigation
plants were only partly realised but social conditions got worse than in the case of the Aral Sea
because the growth of the population was too fast
and the 17 million people living around the lake
were too much for the natural environment. As a
result 4.5–7.0 million people are starving depending on crop yields varying from year to year.
Social conflicts also make the situation worse
contributing also to the intensification of international migration. UN launched a 19-milliondollar programme with the support of DP Global
Environmental Facility to save the remnants of
the lake achieving only partial results so far.
Regarding lakes with closed water system
the following general lessons can be drawn.
Serious ecological, economic and social processes take place as a result of water overuse:
species disappear, economic branches collapse
(fishing, canning), poverty grows, migration
starts, etc. That is, life in the given region
becomes unsustainable.
Human disturbance that had negative feedbacks later on the life of the society took place in
the case of almost every major lake and sometimes such activities are unfortunately still going
on. In Lake Victoria, the largest lake in Africa
inflowing sewage causes eutrophication on the
one hand and on the other hand proliferating Nile
perch introduced to supply fish causes unwanted
changes in the ecological system of the lake as
several species disappeared. The authors note
that it is generally better to avoid such problems
than recovering damage. Practice also proved
that prevention is always the cheaper way.
There are some areas on Earth where the water
budget of lakes changed in a positive direction.
Most well-known is the Tibetan Plateau where
temperatures rose by around 0.3 °C per decade on
average in the last three decades. As a result, more
snow and ice melted than before. The area of the
4 Changes on Earth as a Result of Interaction Between the Society and Nature
tant areas making soil unproductive and destroying pastures. Once thriving fishing produced
40,000–50,000 tonnes of fish each year for the tin
factory on the coast of the lake. Nowadays fish
recovery is reduced to 1000 tonnes per year and
60,000 fishermen lost their job. Life has been
almost completely perished from the lake, a real
ecological catastrophe can be witnessed making
even the economy of the surrounding countries
suffer. In 1995 Kazakhstan, Kyrgyzstan,
Tajikistan, Turkmenistan and Uzbekistan agreed
to save the remnants of Aral Sea. In 1997 UNEP
(International Fund for Saving the Aral Sea) and
later the World Bank supported financially the
works. A rehabilitation plan called INTAS Project
was prepared by 2006 stating the changes
required in the complete water system of the lake.
Regarding the plans the Kokaral Dam has
been realised with 86 million dollars of World
Bank support improving the water supply of the
remaining northern part of the Aral Sea as Syr
Darya supplies enough water for the rehabilitation of the North Aral Sea. Water level was raised
at a relatively rapid rate and the salt content of
North Aral Sea increased to 8–13‰ by 2018, i.e.
reaching the level of the 1960s. It seems likely
that the complete loss of the large lake can be
hindered; however, retrieving the original conditions (typical for the 1960s) is highly unlikely.
Warming climate threatens the glaciers supplying
Amu Darya and Syr Darya thus probably the
water supply of the Aral Sea will decrease.
Numerous lakes have similar problems like
the Aral Sea affecting of course people living on
their coast and in their catchment area.
Occasionally natural and social reasons together
threaten the water system of a large lake. An
example for this is Lake Chad in Africa (Coe and
Foley 2001) that is located in somewhat better
climatic conditions: although annual precipitation is only 300 mm in its northern part but in the
south annual precipitation exceeds 650 mm.
These average values hide extremely variable,
prolonged dry and wet periods. There are several
countries in the drainage basin of the lake.
Nigeria, Chad and Cameroon initiated irrigation
programmes in the 1970s in order to, among others, achieve adequate crop yield in a long dry
period. Especially the plans of Nigeria were
ambitious: 67,000 ha were planned to be irrigated
in the catchment area of the lake. The water system of the lake was further strained by a series of
settlements built on its coast using its water. The
result resembles the Aral Sea: rapidly retreating
water surface as the depth of the lake was small.
Open water disappeared by the 1980s as it was
covered by aquatic plants. Worryingly many nonnative species appear among the plants. Irrigation
plants were only partly realised but social conditions got worse than in the case of the Aral Sea
because the growth of the population was too fast
and the 17 million people living around the lake
were too much for the natural environment. As a
result 4.5–7.0 million people are starving depending on crop yields varying from year to year.
Social conflicts also make the situation worse
contributing also to the intensification of international migration. UN launched a 19-milliondollar programme with the support of DP Global
Environmental Facility to save the remnants of
the lake achieving only partial results so far.
Regarding lakes with closed water system
the following general lessons can be drawn.
Serious ecological, economic and social processes take place as a result of water overuse:
species disappear, economic branches collapse
(fishing, canning), poverty grows, migration
starts, etc. That is, life in the given region
becomes unsustainable.
Human disturbance that had negative feedbacks later on the life of the society took place in
the case of almost every major lake and sometimes such activities are unfortunately still going
on. In Lake Victoria, the largest lake in Africa
inflowing sewage causes eutrophication on the
one hand and on the other hand proliferating Nile
perch introduced to supply fish causes unwanted
changes in the ecological system of the lake as
several species disappeared. The authors note
that it is generally better to avoid such problems
than recovering damage. Practice also proved
that prevention is always the cheaper way.
There are some areas on Earth where the water
budget of lakes changed in a positive direction.
Most well-known is the Tibetan Plateau where
temperatures rose by around 0.3 °C per decade on
average in the last three decades. As a result, more
snow and ice melted than before. The area of the
4 Changes on Earth as a Result of Interaction Between the Society and Nature