LOS ANGELES, March 8 (Xinhuanet)-- The majority of the world's population will soon live in urban rather than rural areas, researchers at the Earth Institute of Columbia University said Tuesday.

    A new study finds that as much as 3 percent of the Earth's land area has already been urbanized, which is double previous estimates.

    The new data collection, known as the Global Rural Urban Mapping Project (GRUMP), has provided the basis for a number of important insights not previously known.

    The following are a few key features that the GRUMP data has showed:

    -- About 20 percent of the world's urban settlements have populations below 500,000. This is an important finding considering that the UN Population Division only reports on urban settlements of 500,000 inhabitants or more.

    -- Roughly 3 percent of the Earth's surface is occupied by urban areas, an increase of at least 50 percent over previous estimates that urban areas occupy 1 to 2 percent of the Earth's total land area.

    -- Coastal environments have much higher concentrations of urban land area, at 10 percent, and urban populations, at 65 percent, than other ecosystems.

    -- Far fewer Asian and African urban residents live in coastal and cultivated areas than residents of the Americas, Europe and Oceania, but population densities in coastal cities of Asia and Africa are much greater than those on other continents.

    -- Approximately 7 percent of urban dwellers now reside in the world's largest mega-cities, whereas experts had previously estimated this number to be around 4 percent.

    -- Tokyo, including more than 500 connected settlements, is thelargest urbanized area in the world at 30,000 square km.

    "The GRUMP data sets will allow us to rethink trends in urbanization and the relationship between population, ecosystems and land use," explained Deborah Balk, the principal investigator of GRUMP.

    The study has resulted in the construction of a suite of products constituting the first detailed and systematic data sets on urban population distribution and the extents of human settlements across the globe.

    Although population census and satellite data have been available for some time, until now minimal effort had been made tocombine these two kinds of information to capture the geographic boundaries of human settlements.

    The GRUMP data collection consists of three individual databases that build upon population data sets mostly from national statistical offices, satellite data and other representations of settlements.

    In contrast, prior data sets such as those from the United Nations or the Digital Chart of the World indicated either the population size or extent of urban areas, but not both.

    These findings will contribute to the global endeavor to alleviate poverty, other scientists said.

    "Past spatial population data sets have confounded urban and rural populations," said Stanley Wood, head of the Spatial Analysis Research Group at the International Food Policy Research Institute.

    "But the better we can distinguish patterns of rural population,farming and use of natural resources, the better placed we are to address the major challenges of rural development and poverty alleviation. GRUMP is an important step in the right direction."

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