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Nature reflects our nature
High altitude lakes as indicators of environmental
changes: a palaeolimnological perspective
Lakes located above treeline are called high altitude lakes. These lakes are characterized by a set of unique
physico-chemical and biological features which set them apart from other waterbodies. They are often locat-
ed in small catchments with slow weathering bedrock; and characterized by a thin topsoil layer supporting
sparse vegetation, short ice free period, high UV penetration. Accordingly, these water bodies often tend
to have low conductivity values, low nutrient concentrations and dissolved organic carbon; with short food
chains. They provide a range of crucial ecosystem services for local as well as downstream communities.
Because of their remoteness, high altitude lakes are less affected by local sources of pollution and thus
these ecosystems are often used as reference sites to evaluate changes elsewhere and many studies have
emphasized their importance as sensors of global environmental changes. Moreover, their bottom sediment
deposited over time stores important information of the past environmental conditions. These information
are present in the form of fossilized diatom valves, chironomid mouth parts, pollens, chrysophycean starch,
Cladocera; organic matter content, isotopes and geochemistry. These components act as proxies of lake
and catchment history and thus can be used to reconstruct long as well as short-term past environmental
conditions and associated environmental changes in Palaeolimnological studies. Paleolimnological studies
involve extraction of lake bottom sediment cores, slicing of the cores into sub-samples, establishment of
sediment chronology and analyses of physical, chemical and biological proxies in the sediment cores to infer
past environmental changes. A number of such studies have been carried out in lakes worldwide to quantity
the observed changes in pH, organic pollutant contamination, nutrient concentrations, fluctuations in lake
water levels. Such information are essential not only for past environmental reconstruction of lakes and their
catchments but also for defining reference conditions of the lakes; current status and trends of environ-
mental changes; identifying the causes of such changes in defining restoration targets thereby helping in
developing future strategies for proper lake and watershed management.
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Smriti Gurung, Ph.D, Assistant Professor
Department of Environmental Science and Engineering,
Forest soils are important sinks for methane, but can hu-
man use of forests reduce their efficiency?
Forest soils are known to act as sinks for atmospheric methane, a major greenhouse gas. Methane is the
most abundant organic trace gas in the atmosphere, primarily created by biological processes of microbes
(methanogenesis). It plays an important role in global climate change, and forest soils are known to be ef-
fective sinks for methane. In soils, methane is primarily utilized by bacteria that oxidize it to produce carbon.
However, the effectiveness of soils as sinks is affected by land-use practices such as agriculture, and forest
or woodland soils are considered more effective sinks than soils in human landscapes. Forests are increas-
ingly affected by anthropogenic influences such as animal grazing, forest fires, etc. by the people living in the
vicinity of the sanctuary. Treading and trampling by grazing animals leads to soil compaction, especially in
wet tropical conditions. Soil compaction decreases the number of soil pores, in turn decreasing soil aeration.
The condition of reduced soil pore volume and increased water-filled pore space reduces the ability of soils
to absorb methane.
During the monsoon, grazing activities are lower due to heavy and prolonged rainfall, which will lead to higher
methane sink. While higher grazing pressure during the post-monsoon season leads to reduced methane
sink. While human practices are known to play a role in altering forest sink potentials, disturbances due to
animal grazing can also reduce soil’s methane oxidation potential, hence reducing the overall methane sink
strengths of soils in forestland
Nani Raut, Ph.D, Assistant Professor
Department of Environmental Science and Engineering
Nature and Social Concern Society
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