GLOBAL ENVIRONMENTAL CHANGE AND VULNERABILITY OF ECOSYSTEMS: FROM LOCAL TO REGIONAL AND GLOBAL SCALES
Mečislovas Žalakevičius
Institute of Ecology, Akademijos 2, 2600 Vilnius, Lithuania; e-mail:
Key words: climate change, global warming, bird migration, population state, breeding range shift, distribution areas, vulnerability of ecosystems
Many processes occurring on the Earth are climate-related. Seasonal fluctuation in temperature determines the existence of the Earth's climatic zones and ecosystems, which have a unique environment with specific plants, animals, and precipitation amount.
Air temperature in the last two hundred years was not stable around the world and in the Baltic region as well. Since XIX century the mean annual temperature has increased approximately by 1 o C in Lithuania, and in the course of XX century – by 0.7 o C. The registered temperature increase in winter and spring seasons during this period was more apparent, whereas changes in summer and autumn seasons were not so obvious. Increase in mean air temperatures in winter and spring seasons has been more significant since the 1960s (up to 1.7-2 o C).
Recent global environmental change raises new problems and targets for ecology and human being. This process covers the entire planet. Under the effect of global warming the world suddenly became small. Unfortunately, the consequences of the planet's warming have not received sufficient investigation yet, while this kind of research is of both theoretical and practical importance. Under the above mentioned circumstances research into biodiversity and dependence of different characteristics of flora and fauna upon changing environmental temperatures, as well as the related modeling is crying out for attention.
Due to universal processes, that regulate functioning of ecosystems with wildlife as one of its components, local investigations have assumed not only narrow regional but also international importance and application. So, results of local research activities can be successfully adapted on a regional or global scale. Science does not recognise frontiers. It is similar to birds which breed in certain countries, feed and accumulate fat deposits for migration in other countries and winter in the third countries, migrating over large territories and continents.
Human being is closely related to wildlife and depends on its state. Ecosystem is as a living organism the components of which are closely interrelated. Thus even the slightest environmental alteration can result in a negative feedback for all the mankind and its future generations. Not without reason such great attention has been recently paid to environment and wildlife conservation in the world.
Recently the effect of climate change upon wildlife has become obvious and this effect has significance for different branches of economy: civil and military aviation, agriculture, forestry, environmental protection, fishery, transport and hunting. Herein we deal with sensitivity and vulnerability of the country or region.
Among the indications of climate change impact on wildlife the following can be mentioned: changes in bird population state or trends, their breeding ranges, staging and wintering territories. They are of extreme importance for environmental protection and different sectors of economy not only in Lithuania, but in the Baltic region, Europe and all over the world as well. Here I must stress that changes in wildlife first of all are expressions of changes in habitats and ecosystems. Wildlife could be used as an indicator of global climate change and anthropogenic impact. Reclamation of lands and forests, canalization of rivers and streams, increasing thermal and chemical pollution, expansion of seaports and transport infrastructure have become crucial to birds in the process of global climate change.
Efforts are made to preserve wildlife, its habitats and ecosystems for humanity and its forthcoming generations by allotting sufficient financing for that purpose. Large amounts of international money resources are assigned for environmental protection whereas global processes taking place in the world bring changes into the possibilities to preserve biological diversity in certain earlier designated strictly protected territories.
My presentation deals with the impact of global warming on wildlife which is based on the example of the avian annual cycle: timing and characteristics of migration, breeding, staging, and wintering.
Bird migration.
It is known that bird strikes as a rule are registered in civil and military aviation during bird migration periods and on migration territories. Different kinds of forecasts are applied to prevent this great danger.
Our results of recent investigations (performed from 1966 up to 2001) indicate that under the conditions of more expressed global warming (1990-2001 in Baltic region) 85% of short-distance migrant species investigated in spring and 74% of investigated long-distance migrants arrived at the Žuvintas Strict Nature Reserve much earlier. This regularity was reiterated in Vilnius environs: 88.2% of short-distance and 82.8% of long-distance migrant species arrived in spring earlier. As you know long-distance migrants winter in Africa, short-distance migrants - in Western Europe and in Mediterranean region. This regularity was statistically significant in 26.7% cases for short-distance migrant species and in 58.3% cases for long-distance migrants (p<0.05-0.001).
The study of spring arrival into the entire territory of Lithuania (to more than 130 sites of registration), as well as Central and Eastern Europe shows that the course of arrival of the selected model species (Skylark, Starling, White Stork, Swallow, and Cuckoo) directly depends upon the rise in air temperature. Higher temperatures were associated with earlier arrival (a significant relationship was obtained in four species: p<0.01-0.001).
Migratory take-off.
Undoubtedly, of all migration processes and its constituent parts the most sensitive to climate change is migratory take-off. We defined that birds try to take off under particularly favourable and ideal for the flight conditions. It helps them to avoid extreme flight conditions in a great part of their migratory passage.
We established that the take-off with subsequent migration of maximum and high density associated with increasing air temperature in spring and with falling air temperature in autumn. Furthermore, the greater the increase in air temperature in spring and the greater the fall in autumn, the greater the density of the take-off. Thus climate change induces certain shifts in take-off periods, influencing alterations in staging areas and formation of bird accumulations in them, and eventually conditioning the timing and number of migration waves, migratory distances, and species characteristics of migratory course.
Bird migration control.
In bird migration control, climate change acts both through the endogenous programme, readiness for flight, changing its periods, and through changes in environmental conditions. The existing models with the set-up range of transition from the endogenous programme to the environment and vice versa may shift to one or another side. Thus bird migration control may only change the ranges of dynamic balance, which are essential for the practical use of the mechanisms controlling migration.
Very interesting data were obtained when analysing bird breeding cycle. When verifying the hypothesis of global climate change impact on bird breeding areas, data confirming it were obtained. Besides that, different impact of climate change was established on short-distance and long-distance migrants, breeding in the region of three Baltic states - in the territory eastward from the Baltic Sea.
It is known, that conditions most favourable for the species life and their successful existence are as a rule observed in the central part of their distribution ranges (Timofejev-Resovskij, Jablokov, Glotov, 1973). In that part of ranges, habitats that are most favourable for the species are found, as well as the greatest mean abundance of the population. In the peripheries of ranges, where the complex of abiotic and biotic conditions is often extreme, mosaic-like, fragmentary spread of individuals within the populations is usually observed, thus populations are found in low density. It is confirmed by the analysis of the ranges of the bird species enlisted in the Red Data Book of Lithuania that almost all bird species are outside the limits of their entire distribution ranges - in the periphery of the fragmentary ones. And, the state of as much as 1/3 of the populations of the bird species included in the Red Data Book is stable or they are increasing. The remaining 2/3 of the populations are decreasing in Lithuania. As for the populations of the remaining 147 bird species not included into the Red Data Book of Lithuania, the analysis of their distribution ranges within the Western Palearctic shows that even 57.83% of these species breed in the central part of their ranges and only 42.17% of them breed in the periphery. Populations of 84% of the species not included into the Red Data Book and breeding in the central part of their ranges are increasing and stable and only 16% are decreasing.
The species and populations that expand their ranges in a certain direction show higher population abundance in the periphery of this direction.
So, if the range expanded in the northeastern direction because of climate change the bird populations that are in the northern-northeastern-eastern periphery of their Western Palearctic ranges ought to get under optimal conditions and their abundance ought to increase, whereas in the western-southwestern-southern periphery due to the contracting range the conditions ought to become more unfavourable and population abundance ought to diminish. On testing the above hypothesis it was established that the species which are both included and not included into the Red Data Book of Lithuania show a clear tendency towards a rise in population abundance and stability in the northern-northeastern-eastern periphery and a drop in the southern-southwestern-western periphery of the ranges. These regularities observed in recent years confirm our hypothesis about the impact of climate change on the population ranges of birds breeding in Lithuania.
The species analysed belong to various ecological groups and breed in habitats of various ecosystems. Anthropogenic effect does not explain these differences as it is similar to different species on the investigated territory.
Besides, no differences have been found between sedentary and migratory species.
The above regularities established for Lithuania show that the Western Paleartic ranges of breeding species are undergoing a shift to the northeast. This could be attributed to only one reason: a northward (north-eastward) shift of climatic zones due to global climate change.
During our research an interesting regularity was established: the impact of global climate change or the shift in distribution ranges is better expressed in birds of terrestrial and wetland ecosystems. Meanwhile, in water ecosystems habitats are not so strongly influenced by global climate warming. Water acts as a buffer. This law is interesting not only from the theoretical but also from the practical point of view as far as environmental protection and various branches of economy are concerned. In environmental protection this factor is acute when choosing the areas for the protection of certain species in which the habitat state undergoes changes under the effect of climate warming. The changes in habitat state are followed by the change in the preserved species state. As a result of that, protected areas stop meeting the requirements that they should and therefore their status should be altered. However, that is not an easy task to do.
Analysis of 129 migratory bird species reveals distinct differences between populations of long- and short-distance migrants breeding in Lithuania. It has been established that in the northern part of the ranges short-distance migrants are most abundant among the increasing populations, but in the southern part long-distance migrants predominate in decreasing populations. The populations that are in the central part of the ranges are markedly growing for short-distance migrants, but they are diminishing for the long-distance ones. Statistically significant association between certain parts of bird species ranges and their migratory categories: short- or long-distance was obtained. This attests the hypothesis of some scientists in Europe about different impact of global climate change on short- and long-distance migrants. Short-distance migrants gain from this process eliminating long-distance migrants and reducing their possibilities in competition.
Staging, wintering and migratory-resident state.
One of the signs of climate change impact upon migratory process of birds is the regulation of migratory-resident state, which has developed in the course of evolution as a response to periodical global processes of the rise and fall in temperature, including global warming of recent years. Global warming causes shortening of migratory routes of birds breeding in Lithuania, their winter quarters coming close to breeding sites.
Recently shortening of migratory routes of birds breeding in Lithuania has been observed, new wintering sites and new staging concentrations have been determined. Our analysis revealed that the migratory routes of Starling, Mallard, Mute Swan, Merganser, sea ducks, White-fronted Goose, ringed in Lithuania after 1989, to their wintering sites has shortened.
These changes cause quite a number of urgent environmental problems in the Lithuanian coastal zone of the Baltic Sea, where huge accumulations of wintering water birds, that have the status of international protection, have formed. Meanwhile, in this area oil export and import is being expanded, the huge sea oil terminal has been constructed, the sea port is being extended and fishery is intensifying. All the above mentioned factors have a disastrous effect on wintering water birds – many of them perish here.
So, in this work, a new viewpoint of Lithuanian ornithologists on the global processes occurring on the planet and in the country is reflected. Until now the bird distribution and population change were related first of all to other reasons (such as habitat succession, anthropogenic loading, land-reclamation, agricultural practices, environmental pollution, resource utilisation, etc.). However, these reasons are not the only and the most important factors. After the volume of land-reclamation works in Eastern Europe had been reduced and intensive collective agriculture had been destroyed, industrial and agricultural pollution became less intense and the areas of monocultures decreased.
Unfortunately, global climate change impact on wildlife and biodiversity has been so far insufficiently investigated. The perspective of such research is evident. We hope that this subject will not be avoided by researchers, and new valuable results will be obtained in the future.
So, in conclusion we must recognize that global warming impact on wildlife influences economic activities, and raises new environmental problems. Due to the sustained warming of winter seasons, the majority of species have shifted east- and northwards; the main stop-over areas of migrating populations have changed; the number of resident birds in different populations is rapidly increasing, the migratory distances have diminished. These changes reveal new urgent practical ecological problems on the science-policy interface basis. They are the audit of the net of old strictly protected areas, establishment of new protected areas, optimisation of the usage and protection of biological diversity and its resources, land privatisation and use practices, new commitments in relation to the international conventions, revision of ecological preservation strategies, action plans and programmes. Knowledge of these changes has a direct influence on success in the bird strike problem management: ways of solution, applicability of concrete measures, their effectiveness, etc.