Global Data Hound

In this month’s TerraViva! spotlight is a global map of human impact on marine ecosystems that was created by the National Science Foundation’s National Center for Ecological Analysis and Synthesis (NCEAS) at the University of California at Santa Barbara. The map is based on a study that was published in the February 15, 2008 issue of Science (Halpern, B.S., et al. A Global Map of Human Impact on Marine Ecosystems, 15 February 2008, Science 319, 948 (2008).) The study is significant because it is the first-ever spatially explicit global assessment of human impacts on marine ecosystems.

The strategy for building the human impacts map was to estimate the global impact of 17 different types of (at least partially) anthropogenic drivers –such as oil rigs, invasive species, and fisheries — on 14 types of marine ecosystems — such as beach, coral reefs, and deep waters.The driver layers were rescaled to unitless values between 0 and 1. Then an expert survey provided weighting variables by assessing the vulnerability of each ecosystem type to each driver on five different ecological criteria. The weighted 0-1 driver impacts for each 1 km sq cell were summed and the final number represented the relative cumulative impact of human activities on all ecosystems in a particular 1 km sq cell.The techniques used to create each data layer are described in detail in the supporting online material published in Science, which, for a global data hound, is the equivalent of a bunch of juicy steaks. Often, substantial cleverness was involved. For example, oil rigs at sea were identified using the Stable Lights of the World data set from NOAA/DMSP. Invasive species were modeled as a function of the amount of cargo traffic at a port, based on peer-reviewed scholarly articles establishing a relationship between the variables and port traffic estimated using several port databases from the American Association of Port Authorities, Australia, Lloyd’s, and the National Geospatial Intelligence Agency. (I was thrilled to find out about the additional port databases as I had to rely on Digital Chart of the World’s port layer for a project a couple of years ago and was frustrated with its age and lack of detail about ports). Fisheries impacts were based on half-degree global commercial catch data developed by the Sea Around Us Project. In short, if you need global ocean data, this is a great place to start!

Here is a global view (at 20 arc minutes) of the summary data:

This is a useful synoptic view of the situation. What it seems to show is that there are substantial human impacts on the oceans in most of the world and that there are particularly severe impacts in highly developed coastal fisheries. It is interesting to compare this view of ocean impacts with this view of “the human footprint” on land, produced by SEDAC:

and with this view of Ocean Primary Productivity 1997-2002 from NASA.

It’s not surprising that human impacts are high in areas where there is high ocean primary productivity, but note that the east and west coasts of Africa and South America have relatively high primary productivity with, as yet, less intense human impacts..  One wonders whether human impacts on these coastlines will increase over time.

We used an alpha feature in Global Data Analyst to prepare the following map, which combines the Human Impact on Marine Ecosystems with the SEDAC Human Footprint to provide a unique view of human impact on the world.

This version of the integrated map combines two separate color schemes.  In both land and sea areas, reds mean high human impact, while at land green means less impact and at sea pale yellow means less impact.  The overall impression of “busy-ness” caused by the clashing color schemes is not far from the truth, as we know from pictures of human debris washed up on isolated beaches hundreds of miles from the nearest human habitation.

(Kure Atoll, NW of Hawaii, 2006)

Most of Earth, including both land and oceans, is significantly influenced by human activity.

P.S. The map files for the TerraViva! viewer can be downloaded from ISciences in two versions: a smaller one (49 MB) that contains maps at resolutions of 2 arc minute, a 5 arc minute, and 20 arc minutes , and a larger one (289 MB) that also contains a 30 arc-second map.