Geoscience Reference
In-Depth Information
for up to seven months of the year, with a per-
mafrost layer
from intensive human activity. The greater Lena
basin, however, is rich in natural resources
including gold, other metals and coal that have
been exploited commercially. While there are no
settlements within the delta itself, hunting and
i shing are common. The closest town to the
delta is Tiksi, an important coastal port city on
the Laptev Sea. In 1985, the Lena Delta Nature
Reserve, also known as the Ust-Lensky Zapoved-
nik, was established to protect this tundra land-
scape and habitat (Center for Russian Nature
Conservation 2011). The greatest short-term
threat to this delta is its vulnerability to the
impacts of climate change. These impacts may
include higher average winter and summer tem-
peratures, thawing of the permafrost, and the
effect of more frequent and catastrophic l ood
events upstream on the Lena.
With warmer temperatures recorded across
the Arctic in the past 20-40 years (McBean
et al. 2005), greenhouse gas emissions from
sequestered sources in northern permafrost
regions have been a growing concern. Northern
latitude wetlands already contribute signii cant
methane emissions. It is expected that thawing
permafrost would speed up the decomposition
of organic matter, enhancing microbial activity
and methane releases. Across the Russian Arctic
including the Lena basin, the thawing of yedoma,
an organically rich permafrost with a high
carbon content, is also a matter of concern
(Sachs et al. 2008). The natural release of
methane and other greenhouse gases from
degraded thermokarst landscapes in northern
latitudes over the coming decades and centuries
is expected to amplify feedback on the climate
system.
Studies suggest that there has already been
some permafrost degradation of Arctic coastal
lowland regions around the Lena basin (Grosse,
Shirrmeister and Malthus 2006). Thawing per-
mafrost and warming temperatures could have
signii cant impacts on the Lena Delta. Enhanced
erosion from wave action along the delta
front may occur due to the loss of permafrost,
while increased temperatures and further
thawing could enhance methane releases or
drain the thermokarst landscape (Anisimov et
al. 2007). Such changes across the Arctic would
500 m deep and a mean annual
temperature of
>
13 °C (Schneider, Grosse and
Wagner 2009). Yet, as the active layer, extending
just 10-100 cm below the surface, melts during
the brief summer, the region turns into a bio-
logically rich wetland oasis for tundra vegeta-
tion, birds and mammals (Center for Russian
Nature Conservation 2011).
Data from several studies combined have
reported 122 total bird species in the delta,
which is one of the highest numbers of any
region this far north of the Arctic Circle (Gilg et
al. 2000). Among other factors, studies attribute
this high species diversity and terrestrial and
marine productivity to the mixing of the Lena's
warmer fresh water and sediments into the cold
Laptev Sea (Gilg et al. 2000). Mammals found
in the delta include voles, Siberian lemmings
(
Lemmus sibiricus
) and collared lemmings
(
Dicrostonyx torquatus
), which provide an
important source of food for other predators
and birds such as the snowy owl (
Nyctea scan-
diaca
) (Gilg et al. 2000). The Arctic fox (
Alopex
lagopus
) and reindeer (
Rangifer tarandus
), are
among the other species observed in the delta
(Center for Russian Nature Conservation 2011).
An image from Landsat's Thematic Mapper
sensor shows a summer landscape that is typi-
i ed by thousands of channels, islands, sand
bars, patterned tundra and water-i lled depres-
sions, along with grasses, sedges, lichen and
moss species (Fig. 17-31). The combination of
visible and infrared bands used in this false-
color composite highlights terrestrial and water
boundaries, narrow water channels, soil mois-
ture differences and vegetation type in vivid
detail. As in other wetland sites, the presence
of water inl uences vegetation coni gurations
across the Lena Delta (Schneider, Grosse and
Wagner 2009). Water-saturated areas are domi-
nated by sedges (
Carex aquatilis
). Grasses and
mosses are found on poorly drained moist soils,
whereas dwarf shrubs and water-intolerant
grasses are found in drier areas. This geographic
landscape provides ideal waterfowl and shore-
bird breeding, nesting and foraging habitats.
Given its remote location and forbidding
climate, the Lena Delta has largely been spared
−
