Since 1861, when systematic recording of meteorological data began, the global average temperature has increased by 0.6°C (+/- 0.2°C). The average surface temperature of the northern hemisphere over the past centuries is likely to have risen at a higher rate than it did in similar periods over the last 1000 years. Experts argue that, by 2100, temperatures might rise by 1.4 to 5.8°C relative to 1990 (IPCC 2001)- a rise that exceeds all natural temperature fluctuations observed during the past few centuries.
Moreover, these processes are extraordinarily dynamic, with temperature changes occuring at a speed never before seen, in the the last 10,000 years.
Climate change in Austria
In Austria temperatures went up by 1.8°C during the 20th century; a trend that was observed at all altitudes. A further climate-induced rise in the average annual temperature is projected, with the temperature rise observed in the Alpine area being significantly above the global average.
Research findings by the Hadley Centre in Great Britain predict an increase in summer temperatures by 5 to 11 degrees in the western parts of Austria - a rise that, by far, exceeds earlier projections. Further, the findings regarding precipitation pattern was inconclusive, with the level and distribution of rainfall differing greatly between the individual climate models used.
Climate change also alters precipitation patterns
Changes in rainfall patterns will probably differ widely between regions. Generally speaking, extreme weather events, such as storms, dry periods, and heavy precipitation, are expected to occur more frequently. Moreover, as the impacts of man-made climate change are already being felt, and are only expected to get worse in the coming decades, the microclimates found within forests will drastically change in both the immediate and distant future.
As a result, there is some doubt over the extent of the impact forestry can have on mitigating the effects of climate change. Nevertheless developing and implementing measures, such as planting specially chosen tree species, improving the structure of forest stocks, and implementing various operational plans to ensure that forests can adapt to the impacts of climate change is an urgent necessity.
Study: Impacts of climate change in Austria
A 2001 study by Lexer et al explored the consequences that would emerge in Austria, should the average temperature increase by 2°C and should the total volume of rainfall reduce by 15%- thereby simulating the effects of one model of climate change. Their results, up to the year 2050, give the following expectations:
It is highly likely that, during the next few decades, the higher temperatures will result in the death of numerous trees and tree species at low-altitude areas, as they will no longer be able to grow. This is especially true for secondary spruce forests that are found in low-altitude areas and, as a result, the regulated management of these spruce stands, which even now are often inappropriate for the location they are grown in (due to temperatures), will no longer be possible. That said, due to forward-thinking forest management policies, such forest stands account for only a small percentage of the overall forest area.
Furthermore, the results of modelling suggest that short- to medium-term impacts will be less evident at higher altitudes. These calculations are based on the assumption that the productivity of forest stands would rise.
The projected long-term effects of this particular scenario will be more pronounced in high-altitude areas than at lower altitude areas . This is due to the fact that, in the warmer conditions that will emerge, deciduous trees will now be able to compete with the currently dominating conifers- thereby giving forest managers a more diverse range of tree species to plant, since they can now grow in the warmer conditions
In low-altitude areas, where temperatures are higher already, beech trees will continue to be one of the potential natural tree species; the competitive strength of oak will rise compared to beech.
The risk of desertification is realistic only for a small number of sites that are already experiencing extreme weather conditions. However, dry areas are very sensitive even to minor changes in precipitation regimes.
New forest management practices?
Scientific research can, and should, provide a basis for planning and decision-making in forest management. This can be achieved through dynamic simulation models, or computer models that are used to determine how the behaviour of a system over a certain amount of time, of forest ecosystems, as they allow individuals to make quantitative assessments regarding the effectiveness of particular policies. Yet, one must always contextualise any conclusion drawn from modelling as some forest ecosystems have taken a very long time to become what they are today. Current forecasts suggest that climate change is occuring at a very fast rate, which results in the emergence of certain fears, such as that the changes are occuring too quickly for the natural adaptive capacity of forest ecosystems to ensure their stability or ecological functioning- or even that forest will no longer be able to perform their various roles in the facilitation of natural cycles.
The constantly changing climate is a great challenge for forestry. On the one hand, there are elements of uncertainty in all forecasts, while on the other extreme individual events can change projected trends and estimates dramatically. Due to knowledge deficits and natural factors, the scope and effectivness of silvicultural adaptation measures over the short, medium, and long term are limited.
Current and previous experience suggest that both near-natural forest stands and forests based on natural selection with species that are suitable to their sites can adapt to their environment more effectively than artificially established forest stands comprising non-native tree species. There are diverging views among experts as regards the potential advantages and disadvantages of cultivating alien, non-indigenous tree species. (Source: The Austrian Forest Programme)