The Biosphere we created: 1700 to 2000

“So how did the biosphere become anthropogenic anyway?” asked an astute audience member at my 2007 AGU presentation (powerpoint). I had just given a presentation on my work with Navin Ramankutty demonstrating that human populations and their use of land have reshaped most of the terrestrial biosphere into anthropogenic biomes, or anthromes (Ellis and Ramankutty 2008).

Great question! I had no real answer then- our work used only data for the year 2000. Now, the anthromes working group has completed its first historical analysis of global changes in anthromes and biomes before and during the Industrial Revolution, from 1700 to 2000, with results published today in Global Ecology and Biogeography (Ellis et al. 2010). The work turned out to be harder than expected, requiring a complete retooling of the original anthromes classification system (anthromes 1, to anthromes 2), and new global historical reconstructions of irrigated and rice areas. But it was definitely worth it!

To begin with, we found that even in 1700, slightly more than half of the terrestrial biosphere was already transformed by humans, though mostly at a relatively low level, creating seminatural anthromes across 45% of earth’s ice-free land and used anthromes across 6%, leaving 49%of earth’s land as wildlands. Used anthromes include the dense settlements, villages, croplands and rangelands anthromes.

Perhaps more importantly, we can now point to the 20th century as a time period in which most of the biosphere (55%) came to be transformed by human populations and their use of land – heralding the end of the wild biosphere and the emergence of a human-managed anthropogenic biosphere; yet another indicator that we have entered the anthropocene. Another discovery was the global importance of novel ecosystems (Hobbs et al. 2006)- the ecosystems we’ve created as a byproduct of our widespread use of land. Our analysis reveals that 37% of earth’s terrestrial ecosystems are now comprised of the remnant, recovering and more lightly used novel ecosystems that have become embedded within used lands- forming the mosaics of used and seminatural ecosystems that we now see covering most of the planet. Wildlands remain on just 22% of earth’s land and are mostly in the tundras and deserts that we humans have little interest in using.

So, how did the biosphere become anthropogenic anyway? In a nutshell, humans changed things gradually before the Industrial Revolution, with changes accelerating in the 20th century, both by the expansion of pastures and crops into new areas and by increasing the use of land within areas used only lightly in the past.

And that is not the final word. Global histories of land use and population, like the ones we used for our analysis, are based on very limited data and fairly rough models, and are being improved all the time. New global land use datasets are being developed that indicate that human use of land may have been far more extensive at much earlier times- most of the terrestrial biosphere may have been transformed by humans long before the 20th century- maybe even by 3000 years ago! (Kaplan et al., accepted). So this may turn out to be a much longer story!

Have a look at the biosphere we created: maps, google earth and google maps are at:

http://ecotope.org/anthromes/maps/

For more on the work, read the paper (link below) and browse our web site.

UMBC Press Release:
http://www.umbc.edu/blogs/umbcnews/2010/08/umbc_researcher_says_humans_ha.html

References

Ellis, E. C., K. Klein Goldewijk, S. Siebert, D. Lightman, and N. Ramankutty. 2010. Anthropogenic transformation of the biomes, 1700 to 2000. Global Ecology and Biogeography 19(5):589-606. [download]

Ellis, E.C., & Ramankutty, N. 2008. Putting people in the map: anthropogenic biomes of the world. Frontiers in Ecology and the Environment, 6:439-447 [download]

Hobbs, R.J., Arico, S., Aronson, J., Baron, J.S., Bridgewater, P., Cramer, V.A., Epstein, P.R., Ewel, J.J., Klink, C.A., Lugo, A.E., Norton, D., Ojima, D., Richardson, D.M., Sanderson, E.W., Valladares, F., Vila, M., Zamora, R., & Zobel, M. 2006. Novel ecosystems: theoretical and management aspects of the new ecological world order. Global Ecology and Biogeography, 15:1-7 [download]

Kaplan, J.O., Krumhardt, K.M., Ellis, E.C., Ruddiman, W.F., Lemmen, C., & Klein Goldewijk, K. (accepted). Holocene carbon emissions as a result of anthropogenic land cover change. The Holocene