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Earth's Land Mammals: Their Only Hope of Avoiding Extinction
Ceballos, G., Ehrlich, P.R., Soberon, J., Salazar, I. and Fay, J.P.  2005.  Global mammal conservation: What must we manage?  Science 309: 603-607.

What was done
The authors conducted "a global examination of mammal distributions to evaluate conservation priorities based on (i) range size distribution, (ii) global patterns of species richness, (iii) political endemism (i.e., the proportion of species restricted to one country), (iv) the minimum area required to preserve one population or 10% of the range of each species, and (v) conservation conflicts in priority areas."

What was learned
Ceballos et al. report that approximately one fourth of all terrestrial mammal species in the world are at risk of extinction, and that to preserve 10% of the range of each species would require 11% of the planet's ice-free land surface.  In addition, they found that 80% of the specific land area in question has been affected to some degree by agriculture, with 20% of it having lost from 26 to 100% of its natural vegetation to agriculture.

What it means
The loss of land to agriculture appears to be the greatest single threat to the survival of earth's mammals; and in the same issue of Science, Foley et al. (2005) report that "human activities now appropriate nearly one-third to one-half of global ecosystem production."  Others have come to the same conclusion with respect to both land (Tilman et al., 2001, 2002) and water (Wallace, 2000), with Green et al. (2005) wondering how humanity will meet the two- to three-fold increase in food demand that will exist by 2050 without usurping all the land that is currently available to what they call "wild nature."

The only answer to this question that we foresee on the horizon is that after all that man can do to become more efficient and productive in the agricultural arena, he will still fall short of the food production capacity that will be required by 2050, and he will have to rely on the aerial fertilization and water conservation (anti-transpiration) effects of the ongoing rise in the air's CO2 content to make up the difference (Idso and Idso, 2000), in order to preserve some land (which at best will not be much) for earth's wild plant and animal species.  Consequently, if anthropogenic CO2 emissions are not allowed to pursue the course that is dictated by the natural evolution of technological development, i.e., if we mandate the type of CO2 emissions reductions that radical environmentalists want to see enforced and are successful at it, most of earth's wild animals have but a few decades before their only remaining representatives will be those fortunate enough to be incarcerated in zoos, with mammals being some of the first to go.

Foley, J.A., DeFries, R., Asner, G.P., Barford, C., Bonan, G., Carpenter, S.R., Chapin, F.S., Coe, M.T., Daily, G.C., Gibbs, H.K., Helkowski, J.H., Holloway, T., Howard, E.A., Kucharik, C.J., Monfreda, C., Patz, J.A., Prentice, I.C., Ramankutty, N. and Snyder, P.K.  2005.  Global consequences of land use.  Science 309: 570-574.

Green, R.E., Cornell, S.J., Scharlemann, J.P.W. and Balmford, A.  2005.  Farming and the fate of wild nature.  Science 307: 550-555.

Idso, C.D. and Idso, K.E.  2000.  Forecasting world food supplies: The impact of the rising atmospheric CO2 concentration.  Technology 7S: 33-56.

Tilman, D., Cassman, K.G., Matson, P.A., Naylor, R. and Polasky, S.  2002.  Agricultural sustainability and intensive production practices.  Nature 418: 671-677.

Tilman, D., Fargione, J., Wolff, B., D'Antonio, C., Dobson, A., Howarth, R., Schindler, D., Schlesinger, W.H., Simberloff, D. and Swackhamer, D.  2001.  Forecasting agriculturally driven global environmental change.  Science 292: 281-284.

Wallace, J.S.  2000.  Increasing agricultural water use efficiency to meet future food production.  Agriculture, Ecosystems & Environment 82: 105-119.

Reviewed 17 August 2005