land classification - Global shapefile of biomes/ecoregions?

I'm looking for a shapefile with this kind of information, only at considerably higher detail. In North America, ecoregions are classified by levels and grouped by vegetation type at much higher detail than on the linked map (which is of similar detail as the 14 WWF biomes). Using that classification, the data I'm looking for should be around level II or level III. E.g. it should differentiate between tropical rainforest, subtropical rainforest, and mangrove forests, and also it should with at least moderate accuracy show the tree line and the snow line in alpine regions.

(I found a WorldGrids raster file at somewhat high detail but it has a couple of problems, e.g. it shows actual vegetation rather than biomes, and I'm really looking for a shapefile anyway.)

Answer

The WWF ecoregions are the original Olsen et al., (2001) classification units. If this is what you are after I would recommend using The Nature Conservancy modification to Olsen that deals with some of the known issues with the original classification.

My preference is the Brown et al., (1998) classification and its Rehfeldt et al., (2012) modification but, it is only available for North America. I would highly recommend against using Bailey's (1983) classification. I have consistently found that incorporating geology into the classification convolves many vegetation and biophysical processes.

There is a relevantly new USGS global ecosystem classification (Sayre et al., 2014) that may be what you are after. The methodology is presented in "A New Map of Global Ecological Land Units — An Ecophysiographic Stratification Approach". The data is available from the USGS Global Ecosystems website.

References

Bailey, R. G. 1983. Delineation of ecosystem regions. Environmental Management 7: 365-373.

Brown, D.E., Reichenbacher, F. and Franson, S.E. (1998). A Classification of North American Biotic Communities. University of Utah Press, Salt Lake City, Utah. 141p.

Olson, D. M., Dinerstein, E., Wikramanayake, E. D., Burgess, N. D., Powell, G. V. N., Underwood, E. C., D'Amico, J. A., Itoua, I., Strand, H. E., Morrison, J. C., Loucks, C. J., Allnutt, T. F., Ricketts, T. H., Kura, Y., Lamoreux, J. F., Wettengel, W. W., Hedao, P., Kassem, K. R. (2001). Terrestrial ecoregions of the world: a new map of life on Earth. Bioscience 51(11):933-938.

Rehfeldt, G.E., N.L. Crookston, C. Sáenz-Romero and E.M. Campbell (2012) North American vegetation model for land-use planning in a changing climate: a solution to large classification problems. Ecological Applications, 22(1):119-141

Sayre, R., J. Dangermond, C. Frye, R. Vaughan, P. Aniello, S. Breyer, D. Cribbs, D. Hopkins, R. Nauman, W. Derrenbacher, D. Wright, C. Brown, C. Convis, J. Smith, L. Benson, D. Paco VanSistine, H. Warner, J. Cress, J. Danielson, S. Hamann, T. Cecere, A. Reddy, D. Burton, A. Grosse, D. True, M. Metzger, J. Hartmann, N. Moosdorf, H. Dürr, M. Paganini, P. DeFourny, O. Arino, S. Maynard, M. Anderson, and P. Comer. (2014). A New Map of Global Ecological Land Units — An Ecophysiographic Stratification Approach. Washington, DC: Association of American Geographers. 46 pages