How much water is on Earth?
Water on Earth, U.S. Geological Survey
The large blue drop represents all of Earth’s water. Diameter is about 860 miles, volume about 332,500,000 cubic miles (1,386,000,000 cubic kilometers.)
The smaller blue drop represents the world’s liquid fresh water. Diameter is about 169.5 miles (272.8 kilometers,) volume 2,551,100 mi3 (10,633,450 km3,) of which 99 percent is groundwater, much of it not accessible to humans.
The smallest blue dot, diameter only 34.9 miles (56.2 kilometers,) volume 22,339 mi3 (93,113 km3) represents fresh water in all the lakes and rivers on the planet. The water life needs every day comes from these precious surface-water sources.
Image Credit: Howard Perlman, USGS; globe illustration by Jack Cook, Woods Hole Oceanographic Institution (©); Adam Nieman.
Data source: Igor Shiklomanov’s chapter “World fresh water resources” in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World’s Fresh Water Resources (Oxford University Press, New York).
How many people live on Earth?
United States population today numbers 313,722,191 (Mon, April 22, 2013, 8:45am PST).
One year ago, on Earth Day 2012, there were 313,465,631 people in USA.
One year ago, we had not reached 7 billion yet. So when did we pass that milestone? The UN officially chose the date of October 31, 2011. The U.S. Census Bureau, which also attempts global population projections, predicts humanity won’t hit the seventh-billion milestone until March 12, 2012, reported National Geographic.
By other estimates, we had not reached 7 billion yet one year ago:
Earth Clock, April 30, 2012
Earth Clock, April 22, 2013
What about growth?
Limits of Growth, revisited
Forty years after the release of the groundbreaking study, were the concerns about overpopulation and the environment correct? Mark Strauss tackles growth
for the Smithsonian magazine, April 2012. Australian physicist Graham Turner
revisited The Limits to Growth (1972) and compared real-world data from 1970 to 2000 with the business-as-usual scenario. Turner, senior research scientist at CSIRO Ecosystem Sciences (previously Sustainable Ecosystems), Canberra ACT, Australia found the predictions nearly matched the facts. “There is a very clear warning bell being rung here,” he says. “We are not on a sustainable trajectory.”
Prosperity without Growth, is it possible?
Tim Jackson, economics commissioner on the UK government’s Sustainable Development Commission, provides a credible vision of how human society can flourish within the ecological limits of a finite planet in his book, Prosperity without Growth: Economics for a Finite Planet.
More Earthday links:
Earth Day Network
15 Facts About Our Planet for Earth Day, Bad Astronomy
Earth Day Photos 2013: The Good, The Bad And The Ugly, Submit your photos to Huffington Post
7 billion: A special year-long series on population from National Geographic magazine, run in 2011.
Dot Earth, Andrew Revkin’s New York Times blog, looks towards 2050 or so, when the human population is expected to reach nine billion, essentially adding two Chinas to the number of people alive today. Those billions will be seeking food, water and other resources on a planet where, scientists say, humans are already shaping climate and the web of life.