NAIROBI, Oct. 31 (Xinhuanet) -- Almost half of the world's lakes are degraded, depleted, or contaminated mainly by human activities,raising important concerns about future water supplies and the fate of species that survive on the water ecosystems, Kenyan President Mwai Kibaki has warned.

    In spite of their immense importance, lakes and other freshwater ecosystems are constantly under threat from the twin problems of water depletion and water pollution, Kibaki said in a message to the 11th World Lakes Conference, which opens here on Monday.

    "The main causes of this damage are inflow of domestic sewage, agricultural runoff, discharge of industrial effluents, over-fishing, introduction of exotic species and habit at degradation as a result of population growth and expansion of cities," he said.

    Sustaining freshwater resources have become one of humanity's greatest modern challenges that call for urgent actions, Kibaki said, adding that practical efforts are required to remedy the damage done and to prevent further damages.

    "The science of conservation has advanced over time, and it is possible to find a balance between the freshwater needs of people and the sustainability of natural ecosystems," he said.

    The 11th World Lakes Conference, starting Monday and ending Friday, brings together more than 500 delegates from around the world.

    The meeting is being held in Africa for the first time and the theme is -- Management of Lake Basins for their Sustainable Use: Global Experience and African Issues. Enditem