Melting glaciers threaten agricultural land
Saturday, 11 August 2007
Fiona Harvey, Environment Correspondent
Melting glaciers will reduce the amount of water available for agriculture in some areas of the world in the future, while rising sea levels will contaminate coastal groundwater supplies, according to scientists studying the effect of climate change on freshwater resources.
Water experts gathered in Stockholm for the international World Water Week conference have been discussing the likely effects of climate change on the availability of fresh water for agriculture and sanitation.
In areas as diverse as California, South America, Uganda and the Himalayas, farming communities often rely on melt water descending from glaciers or snow caps to replenish their rivers and streams in the springtime. But as glaciers retreat in many parts of the world due to global warming, this source of water may no longer be reliable in decades to come.
However, climate change is also expected to increase the amount of rainfall around the world, according to a study published on Friday in the peer-review journal Science, timed to coincide with World Water Week. This effect of this could offset some of the problems of melting glaciers. But if the rain comes in the form of storms, it may further disrupt agriculture.
The study, from the University of Tokyo in Japan, also warned that the timing and volume of spring floods would change substantially. This could lead to more floods, mudslides and dam breaks, with damaging consequences.
Meanwhile, nearly half of the world's population depends on groundwater sources for drinking water and other uses, found the study, but: "Sea level rise will cause saline water intrusion into groundwater aquifers near the coasts and will decrease the available groundwater resources."
The Tokyo scientists warned that these effects, and other problems such as the fact that "the risk of floods and droughts will increase, sometimes in the same region of the world", had not been properly considered in assessments of the world's future water supplies.
A study by the Australian Lowy Institute, released earlier this week, noted that Bhutan and parts of the Andes had already experienced flash flooding where lakes formed from melting glaciers collapsed. In Kenya, the disappearing snows of Mount Kilamanjaro would soon begin to cause problems for agriculture in the highlands, which are dependent on melt water to irrigate crops.
Research from WWF, the environmental campaigning group, suggested that under the future influence of climate change, rivers in the Himalayas, where glaciers are retreating at 10 to 15 metres per year, could be changed into seasonal streams as the area warms. This effect would give rise to freshwater scarcity in the summer months when melt waters contribute the about three quarters of the volume of water in Himalayan rivers.
The group found that in the Ganga river alone, the loss of glacier melt water would reduce river flows from July to September by two thirds, causing water shortage for 500m people and 37 per cent of India's irrigated land. But effects like this are probably still several decades away.
In Tajikistan, in central Asia, ice cover is projected to reduce by a fifth, and ice volume by more than a quarter by mid-century. At first, glacier melting will increase the volume of rivers, but a catastrophic reduction of water flow in rivers will follow, with serious effects on agriculture.
Melting glaciers will reduce the amount of water available for agriculture in some areas of the world in the future, while rising sea levels will contaminate coastal groundwater supplies, according to scientists studying the effect of climate change on freshwater resources.
Water experts gathered in Stockholm for the international World Water Week conference have been discussing the likely effects of climate change on the availability of fresh water for agriculture and sanitation.
In areas as diverse as California, South America, Uganda and the Himalayas, farming communities often rely on melt water descending from glaciers or snow caps to replenish their rivers and streams in the springtime. But as glaciers retreat in many parts of the world due to global warming, this source of water may no longer be reliable in decades to come.
However, climate change is also expected to increase the amount of rainfall around the world, according to a study published on Friday in the peer-review journal Science, timed to coincide with World Water Week. This effect of this could offset some of the problems of melting glaciers. But if the rain comes in the form of storms, it may further disrupt agriculture.
The study, from the University of Tokyo in Japan, also warned that the timing and volume of spring floods would change substantially. This could lead to more floods, mudslides and dam breaks, with damaging consequences.
Meanwhile, nearly half of the world's population depends on groundwater sources for drinking water and other uses, found the study, but: "Sea level rise will cause saline water intrusion into groundwater aquifers near the coasts and will decrease the available groundwater resources."
The Tokyo scientists warned that these effects, and other problems such as the fact that "the risk of floods and droughts will increase, sometimes in the same region of the world", had not been properly considered in assessments of the world's future water supplies.
A study by the Australian Lowy Institute, released earlier this week, noted that Bhutan and parts of the Andes had already experienced flash flooding where lakes formed from melting glaciers collapsed. In Kenya, the disappearing snows of Mount Kilamanjaro would soon begin to cause problems for agriculture in the highlands, which are dependent on melt water to irrigate crops.
Research from WWF, the environmental campaigning group, suggested that under the future influence of climate change, rivers in the Himalayas, where glaciers are retreating at 10 to 15 metres per year, could be changed into seasonal streams as the area warms. This effect would give rise to freshwater scarcity in the summer months when melt waters contribute the about three quarters of the volume of water in Himalayan rivers.
The group found that in the Ganga river alone, the loss of glacier melt water would reduce river flows from July to September by two thirds, causing water shortage for 500m people and 37 per cent of India's irrigated land. But effects like this are probably still several decades away.
In Tajikistan, in central Asia, ice cover is projected to reduce by a fifth, and ice volume by more than a quarter by mid-century. At first, glacier melting will increase the volume of rivers, but a catastrophic reduction of water flow in rivers will follow, with serious effects on agriculture.