Allen et al. (1999) analyzed sediment cores from a lake in southern Italy and from the Mediterranean Sea, developing high-resolution climate and vegetation data sets for this region over the last 102,000 years. These materials indicated that rapid changes in vegetation were well correlated with rapid changes in climate, such that complete shifts in natural ecosystems would sometimes occur over periods of less than 200 years. Over the warmest portion of the record (the Holocene), the total organic carbon content of the vegetation reached its highest level, more than doubling values experienced over the rest of the record, while other proxy indicators revealed that during the more productive woody-plant period of the Holocene, the increased vegetative cover also led to less soil erosion. The results of this study thus demonstrate that the biosphere can successfully respond to rapid changes in climate. As the 15 researchers involved in the work put it, "the biosphere was a full participant in these rapid fluctuations, contrary to widely held views that vegetation is unable to change with such rapidity." Furthermore, their work revealed that warmer was always better in terms of vegetative productivity. Thus, it is likely that future warming in this region may return it to a higher level of biological productivity than what it currently exhibits.
Osborne et al. (2000) used an empirically-based mechanistic model of Mediterranean shrub vegetation to address two important questions: (1) Has recent climate change, especially increased drought, negatively impacted Mediterranean shrublands? and (2) Has the historical increase in the air's CO2 concentration modified this impact? The data-based model they employed suggests that the warming and reduced precipitation experienced in the Mediterranean area over the past century should have had negative impacts on net primary production and leaf area index. When the measured increase in atmospheric CO2 concentration experienced over the period was factored into the calculation, however, these negative influences were overpowered, with the net effect that both measures of vegetative prowess increased: net primary productivity by 25% and leaf area index by 7%. These results, in their words, "indicate that the recent rise in atmospheric CO2 may already have had significant impacts on productivity, structure and water relations of sclerophyllous shrub vegetation, which tended to offset the detrimental effects of climate change in the region."
How can we relate this observation to climate change predictions for the earth as a whole? For a nominal doubling of the air's CO2 concentration from 300 to 600 ppm, earth's mean surface air temperature is predicted by current climate models to rise by approximately 3°C, which equates to a temperature rise of 0.01°C per ppm CO2. In the case of the Mediterranean region here described, the temperature rise over the past century was quoted by Osborne et al. as being 0.75°C, over which period of time the air's CO2 concentration rose by approximately 75 ppm, for an analogous climate response of exactly the same value: 0.01°C per ppm CO2.
With respect to model-predicted changes in earth's precipitation regime, a doubling of the air's CO2 content is projected to lead to a modest intensification of the planet's hydrologic cycle. In the case of the Mediterranean region over the last century, however, there has been a recent tendency toward drier conditions. Hence, the specific case investigated by Osborne et al. represents a much-worse-case scenario than what is predicted by current climate models for the earth as a whole. Nevertheless, the area's vegetation has done even better than it did before the climatic change, thanks to the over-powering beneficial biological effects of the concurrent rise in the air's CO2 content.
Cheddadi et al. (2001) employed a standard biogeochemical model (BIOME3) - which uses monthly temperature and precipitation data, certain soil characteristics, cloudiness, and atmospheric CO2 concentration as inputs - to simulate the responses of various biomes in the region surrounding the Mediterranean Sea to changes in both climate (temperature and precipitation) and the air's CO2 content. Their first step was to validate the model for two test periods: the present and 6000 years before present (BP). Recent instrumental records provided actual atmospheric CO2, temperature and precipitation data for the present period; while pollen data were used to reconstruct monthly temperature and precipitation values for 6000 years BP, and ice core records were used to determine the atmospheric CO2 concentration of that earlier epoch. These efforts suggested that winter temperatures 6000 years ago were about 2°C cooler than they are now, that annual rainfall was approximately 200 mm less than today, and that the air's CO2 concentration averaged 280 ppm, which is considerably less than the value of 345 ppm the researchers used to represent the present, i.e., the mid-point of the period used for calculating 30-year climate normals at the time they wrote their paper. Applying the model to these two sets of conditions, they demonstrated that "BIOME3 can be used to simulate ... the vegetation distribution under ... different climate and [CO2] conditions than today," where [CO2] is the abbreviation they use to represent "atmospheric CO2 concentration."
Cheddadi et al.'s next step was to use their validated model to explore the vegetative consequences of an increase in anthropogenic CO2 emissions that pushes the air's CO2 concentration to a value of 500 ppm and its mean annual temperature to a value 2°C higher than today's mean value. The basic response of the vegetation to this change in environmental conditions was "a substantial southward shift of Mediterranean vegetation and a spread of evergreen and conifer forests in the northern Mediterranean."
More specifically, in the words of the researchers, "when precipitation is maintained at its present-day level, an evergreen forest spreads in the eastern Mediterranean and a conifer forest in Turkey." Current xerophytic woodlands in this scenario become "restricted to southern Spain and southern Italy and they no longer occur in southern France." In northwest Africa, on the other hand, "Mediterranean xerophytic vegetation occupies a more extensive territory than today and the arid steppe/desert boundary shifts southward," as each vegetation zone becomes significantly more verdant than it is currently.
What is the basis for these positive developments? Cheddadi et al. say "the replacement of xerophytic woodlands by evergreen and conifer forests could be explained by the enhancement of photosynthesis due to the increase of [CO2]." Likewise, they note that "under a high [CO2] stomata will be much less open which will lead to a reduced evapotranspiration and lower water loss, both for C3 and C4 plants," adding that "such mechanisms may help plants to resist long-lasting drought periods that characterize the Mediterranean climate."
Contrary to what is often predicted for much of the world's moisture-challenged lands, therefore, the authors were able to report that "an increase of [CO2], jointly with an increase of ca. 2°C in annual temperature would not lead to desertification on any part of the Mediterranean unless annual precipitation decreased drastically," where they define a drastic decrease as a decline of 30% or more. Equally important in this context is the fact that Hennessy et al. (1997) have indicated that a doubling of the air's CO2 content would in all likelihood lead to a 5 to 10% increase in annual precipitation at Mediterranean latitudes, which is also what is predicted for most of the rest of the world. Hence, the results of the present study - where precipitation was held constant - may validly be considered to be a worst-case scenario, with the true vegetative response being even better than the good-news results reported by Cheddadi et al., even when utilizing what we believe to be erroneously-inflated global warming predictions.
Julien et al. (2006) "used land surface temperature (LST) algorithms and NDVI [Normalized Difference Vegetation Index] values to estimate changes in vegetation in the European continent between 1982 and 1999 from the Pathfinder AVHRR [Advanced Very High Resolution Radiometer] Land (PAL) dataset." This program revealed that arid and semi-arid areas (Northern Africa, Southern Spain and the Middle East) have seen their mean LST increase and NDVI decrease, while temperate areas (Western and Central Europe) have suffered a slight decrease in LST but a more substantial increase in NDVI, especially in Germany, the Czech Republic, Poland and Belarus. In addition, parts of continental and Northern Europe have experienced either slight increases or decreases in NDVI while LST values have decreased. Considering the results in their totality, the Dutch and Spanish researchers concluded that, over the last two decades of the 20th century, "Europe as a whole has a tendency to greening," and much of it is "seeing an increase in its wood land proportion."
Working in the Komi Republic in the northeast European sector of Russia, Lopatin et al. (2006) (1) collected discs and cores from 151 Siberian spruce trees and 110 Scots pines from which they developed ring-width chronologies that revealed yearly changes in forest productivity, (2) developed satellite-based time series of NDVI for the months of June, July, August over the period 1982-2001, (3) correlated their site-specific ring-width-derived productivity histories with same-site NDVI time series, (4) used the resulting relationship to establish six regional forest productivity histories for the period 1982-2001, and (5) compared the six regional productivity trends over this period with corresponding-region temperature and precipitation trends. For all six vegetation zones of the Komi Republic, this work indicated that the 1982-2001 trends of integrated NDVI values from June to August were positive, and that the "increase in productivity reflected in [the] NDVI data [was] maximal on the sites with increased temperature and decreased precipitation."
In discussing their findings, the three scientists state that "several studies (Riebsame et al., 1994; Myneni et al., 1998; Vicente-Serrano et al., 2004) have shown a recent increase in vegetation cover in different world ecosystems." What is special about their study, as they describe it, is that "in Europe, most forests are managed, except for those in northwestern Russia [the location of their work], where old-growth natural forests are dominant (Aksenov et al., 2002)." Consequently, and because of their positive findings, they say we can now conclude that "productivity during recent decades also increased in relatively untouched forests," where non-management-related "climate change with lengthening growing season, increasing CO2 and nitrogen deposition" are the primary determinants of changes in forest productivity.
In concluding this brief review of pertinent studies conducted in Europe, we note that within the context of today's obsession with the ongoing rise in the atmosphere's CO2 content, as well as the many environmental catastrophes it has been predicted to produce, the overwhelmingly positive results that have been obtained are truly remarkable. This assessment is even more remarkable in light of the fact that the world's climate alarmists claim the warming of the past quarter-century was unprecedented over the last two millennia or more, and that this phenomenon is the greatest threat ever to be faced by the planet. Apparently the plants of Europe just don't understand the seriousness of the situation.
Aksenov, D., Dobrynin, D., Dubinin, M., Egorov, A., Isaev, A., Karpachevskiy, M., Laestadius, L., Potapov, P., Purekhovskiy, P., Turubanova, S. and Yaroshenko, A. 2002. Atlas of Russia's Intact Forest Landscapes. Global Forest Watch Russia, Moscow.
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Hennessy, K.J., Gregory, J.M. and Mitchell, J.F.B. 1997. Changes in daily precipitation under enhanced greenhouse conditions. Climate Dynamics 13: 667-680.
Julien, Y., Sobrino, J.A. and Verhoef, W. 2006. Changes in land surface temperatures and NDVI values over Europe between 1982 and 1999. Remote Sensing of Environment 103: 43-55.
Lopatin, E., Kolstrom, T. and Spiecker, H. 2006. Determination of forest growth trends in Komi Republic (northwestern Russia): combination of tree-ring analysis and remote sensing data. Boreal Environment Research 11: 341-353.
Myneni, R.B., Tucker, C.J., Asrar, G. and Keeling, C.D. 1998. Interannual variations in satellite-sensed vegetation index data from 1981 to 1991. Journal of Geophysical Research 103: 6145-6160.
Osborne, C.P., Mitchell, P.L., Sheehy, J.E. and Woodward, F.I. 2000. Modellng the recent historical impacts of atmospheric CO2 and climate change on Mediterranean vegetation. Global Change Biology 6: 445-458.
Riebsame, W.E., Meyer, W.B. and Turner, B.L. 1994. Modeling land-use and cover as part of global environmental-change. Climatic Change 28: 45-64.
Vicente-Serrano, S.M., Lasanta, T. and Romo, A. 2004. Analysis of spatial and temporal evolution of vegetation cover in the Spanish central Pyrenees: Role of human management. Environmental Management 34: 802-818.Last updated 4 July 2007