What was done
Because the potential effect of climate change on ecosystems "is a topic of paramount importance," as the authors note, they analyzed a satellite normalized difference vegetation index (NDVI) data set stretching from July 1981 to December 1999 to assess vegetation responses to the different temperature changes experienced concurrently in Eurasia and North America.  This they did via studies of "patch size coherence (Jaeger, 2000), pixel contiguity and clustering (LaGro, 1991), neighborship probability (Riiters et al., 2000), and indices of largest patch (McGarigal and Marks, 1995), and fragmentation (Johnsson, 1995), in addition to basic patch statistics of area, perimeter, and number."

What was learned
With respect to temperature, Eurasia showed an overall warming trend, while North America exhibited a much lower warming rate "and even a slight cooling trend during the last 50 years in the eastern United States."  Specifically, the authors found that "North America shows a skewed distribution of temperature change with a larger fractional area under a marginal cooling trend that is hardly compensated by the area under intensive warming."  Eurasia, on the other hand, showed "mostly a warming trend with negligible occurrence of cooling."

With respect to increasing vegetative prowess, the authors found regions of high NDVI persistence values in Eurasia with high connectivity with large dominant patches, together with higher patch coherence, more pixel clustering, more continuous pixels, more aggregation, and a higher probability of finding orthogonal neighbors.  In North America, on the other hand, they found the spatial pattern of long-term NDVI increases to be fragmented, along with smaller patches, less coherence, higher values of the fragmentation index, less connectedness, pixel remoteness, and a lower probability of finding an orthogonal neighbor.

What it means
The authors say their results "indicate a persistent and spatially extensive and connected greening trend in Eurasia, relative to North America," concluding that "the greening trend in Eurasia is more persistent and spatially extensive than in North America."  These findings are precisely as they should be; for plants actually thrive on higher temperatures in an atmosphere of increasing CO2 concentration (Long, 1991; Idso and Idso, 1994; Cannell and Thornley, 1998).  Hence, we should be thankful for both increasing atmospheric CO2 concentrations and rising air temperatures; for as the real-world data of this study clearly show, rising temperatures greatly amplify the aerial fertilization effect of atmospheric CO2 enrichment.

References
Cannell, M.G.R. and Thornley, J.H.M.  1998.  Temperature and CO2 responses of leaf and canopy photosynthesis: a clarification using the non-rectangular hyperbola model of photosynthesis.  Annals of Botany 82: 883-892.

Idso, K.E. and Idso, S.B.  1994.  Plant responses to atmospheric CO2 enrichment in the face of environmental constraints: a review of the past 10 years' research.  Agricultural and Forest Meteorology 69: 153-203.

Jaeger, J.A.G.  2000.  Landscape division, splitting index, and effective mesh size: new measures of landscape fragmentation.  Landscape Ecology 15: 115-130.

Johnsson, K.  1995.  Fragmentation index as a region based GIS operator.  International Journal of Geographic Information Systems 9: 211-220.

LaGro, J.  1991.  Assessing patch shape in landscape mosaics.  Photogrammetric Engineering and Remote Sensing 57: 285-293.

Long, S.P.  1991.  Modification of the response of photosynthetic productivity to rising temperature by atmospheric CO2 concentrations: Has its importance been underestimated?  Plant, Cell and Environment 14: 729-739.

McGarigal, K. and Marks, B.J.  1995.  Fragstats: Spatial pattern analysis program for quantifying landscape structure.  Gen. Tech. Rep. PNW-GTR-351.  USDA Forest Service, Pacific Northwest Research Station, Portland, Oregon, USA.

Riiters, K.H., Wickham, J.D., O'Neill, R.V., Jones, K.B. and Smith E.  2000.  Global-scale patterns of forest fragmentation (on line).  Conservation Ecology 4(2): paper. 3.