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Glaciers play an important role in the hydrology of
the Andes by storing water in the rainy seasons and
releasing it throughout the year. The proportion of
glacial meltwater in rivers is substantially higher
in the dry season and in dry years (Buytaert et
al., forthcoming). This is due to the lack of rain
and not because of increased melting in the dry
season. Glaciers have a particularly significant effect
downstream in rivers that move into arid areas
towards the Pacific after leaving the mountains.
One extreme example is the Santa River in Peru,
which receives water from glaciers on the Cordillera
Blanca. On average, the contribution of glacial
water in this river is between 4 and 8 per cent
(Ibid.). However, in years with little precipitation
the contribution can be as high as 80 per cent in the
dry season. The compensation effect of glaciers is
particularly important in Bolivia and Peru, where
most tropical glaciers are located: here, there is the
highest difference in seasonal precipitation and
annual precipitation totals are low. In the short term
in the Tropical Andes, diminishing glaciers cause
increased water flow, but in the long term there will
be reduced dry season compensation (Vuille 2013),
which is mainly important for local ecosystems and
mountain communities.
High mountain grass- and wetlands
Grass- and wetlands cover the areas of the high
Andes from the treeline and up to the edge of
the snow. These unique ecosystems include the
neotropical alpine grasslands, known as páramos,
dry and wet puna grasslands and other wetlands.
Páramos cover the upper part of the northern
Tropical Andes and wet punas occupy a similar niche
in the Central Andes. These grasslands, containing
millions of streams, rivers, lakes, and various kinds
of wetlands, are crucial to the hydrology of the
mountains, providing water to tens of millions of
Source: based on Hansen/UMD/Google/USGS/NASA, 2013
Other forest cover
Intact forest landscape*
Forest (2014)
Net forest loss (2000-2014)
Net forest loss (2000-2014)
*De ned as an unbroken expanse of natural ecosystems within the zone of current
forest extent, showing no signs of signi cant human activity and large enough that all
native biodiversity could be maintained
Tropical Andes
BRAZIL
BOLIVIA
PARAGUAY
ARGENTINA
PERU
COLOMBIA
VENEZUELA
ECUADOR
Forest and forest loss extent
Thousands square kilometres
Annual deforestation rate
Forest and forest loss areas
Percentage
2006-2010
2001-2005
0
0,2
0,4
800
100
1
Deforestation in the Tropical Andes region
people downstream. They are also important for
biodiversity and provide carbon storage (Myers et
al., 2000). Carbon stocks in Andean ecosystems are
comparable with those in tropical lowland forests,
especially when organic carbon stocks in the soil
are considered (Spracklen and Righelato, 2014).
Anthropogenic pressure, from agriculture and
climate change in particular, threatens the capacity
of these ecosystems and their services. Páramos are
among the ecosystems most threatened by climate
change, with one biome-based model predicting a
loss of 31 per cent of páramos by 2050 (Tovar et al.,
2013), without including the added threat of land-
use change.