Nadezhda M. Tchebakova

Climate Changes in Siberia

This chapter provides observational evidence of climatic variations in Siberia for three time scales: during the past 10,000 years, during the past millennium prior to instrumental observations, and for the past 130 years during the period of large-scale meteorological observations. The observational evidence is appended with the global climate model projections for the twenty-first century based on the most probable scenarios of the future dynamics of the major anthropogenic and natural factors responsible for contemporary climatic changes. Historically, climate of Siberia varied broadly. It was both warmer and colder than the present. However, during the past century, it became much warmer; the cold season precipitation north of 55°N increased, but no rainfall increase over most of Siberia has occurred. This led to drier summer conditions and to increased possibility of droughts and fire weather. Projections of the future climate indicate the further temperature increases, more in the cold season and less in the warm season, significant changes in the hydrological cycle in Central and southern Siberia (summer dryness), ecosystems’ shifts, and changes in the permafrost distribution and stability. Observed and projected frequencies of various extreme events have increased recently and are projected to further increase. While in the north of Siberia, contemporary models predict warmer winters at the end of the twenty-first century and paleoreconstructions hint to warmer summers compared to the present warming observed during the period of instrumental observations. These three groups of estimates are broadly consistent with each other.

Terrestrial ecosystems and their change

This chapter considers the current state of Siberian terrestrial ecosystems, their spatial distribution, and major biometric characteristics. Ongoing climate change and the dramatic increase of accompanying anthropogenic pressure provide different but mostly negative impacts on Siberian ecosystems. Future climates of the region may lead to substantial drying on large territories, acceleration of disturbance regimes, deterioration of ecosystems, and positive feedback to global warming. The region requires urgent development and implementation of strategies of adaptation to, and mitigation of, negative consequences of climate change.

Potential change in forest types and stand heights in central Siberia in a warming climate

Previous regional studies in Siberia have demonstrated climate warming and associated changes in distribution of vegetation and forest types, starting at the end of the 20th century. In this study we used two regional bioclimatic envelope models to simulate potential changes in forest types distribution and developed new regression models to simulate changes in stand height in tablelands and southern mountains of central Siberia under warming 21st century climate. Stand height models were based on forest inventory data (2850 plots). The forest type and stand height maps were superimposed to identify how heights would change in different forest types in future climates. Climate projections from the general circulation model Hadley HadCM3 for emission scenarios B1 and A2 for 2080s were paired with the regional bioclimatic models. Under the harsh A2 scenario, simulated changes included: a 80%–90% decrease in forest-tundra and tundra, a 30% decrease in forest area, a ~400% increase in forest-steppe, and a 2200% increase in steppe, forest-steppe and steppe would cover 55% of central Siberia. Under sufficiently moist conditions, the southern and middle taiga were simulated to benefit from 21st century climate warming. Habitats suitable for highly-productive forests (≥30–40 m stand height) were simulated to increase at the expense of less productive forests (10–20 m). In response to the more extreme A2 climate the area of these highly-productive forests would increase 10%–25%. Stand height increases of 10 m were simulated over 35%–50% of the current forest area in central Siberia. In the extremely warm A2 climate scenario, the tall trees (25–30 m) would occur over 8%–12% of area in all forest types except forest-tundra by the end of the century. In forest-steppe, trees of 30–40 m may cover some 15% of the area under sufficient moisture.

Northern Eurasia Future Initiative (NEFI): facing the challenges and pathways of global change in the twenty-first century

AbstractDuring the past several decades, the Earth system has changed significantly, especially across Northern Eurasia. Changes in the socio-economic conditions of the larger countries in the region have also resulted in a variety of regional environmental changes that can have global consequences. The Northern Eurasia Future Initiative (NEFI) has been designed as an essential continuation of the Northern Eurasia Earth Science Partnership Initiative (NEESPI), which was launched in 2004. NEESPI sought to elucidate all aspects of ongoing environmental change, to inform societies and, thus, to better prepare societies for future developments. A key principle of NEFI is that these developments must now be secured through science-based strategies co-designed with regional decision-makers to lead their societies to prosperity in the face of environmental and institutional challenges. NEESPI scientific research, data, and models have created a solid knowledge base to support the NEFI program. This paper presents the NEFI research vision consensus based on that knowledge. It provides the reader with samples of recent accomplishments in regional studies and formulates new NEFI science questions. To address these questions, nine research foci are identified and their selections are briefly justified. These foci include warming of the Arctic; changing frequency, pattern, and intensity of extreme and inclement environmental conditions; retreat of the cryosphere; changes in terrestrial water cycles; changes in the biosphere; pressures on land use; changes in infrastructure; societal actions in response to environmental change; and quantification of Northern Eurasia’s role in the global Earth system. Powerful feedbacks between the Earth and human systems in Northern Eurasia (e.g., mega-fires, droughts, depletion of the cryosphere essential for water supply, retreat of sea ice) result from past and current human activities (e.g., large-scale water withdrawals, land use, and governance change) and potentially restrict or provide new opportunities for future human activities. Therefore, we propose that integrated assessment models are needed as the final stage of global change assessment. The overarching goal of this NEFI modeling effort will enable evaluation of economic decisions in response to changing environmental conditions and justification of mitigation and adaptation efforts.

Evaluating the Agroclimatic Potential of Central Siberia

Human beings have traditionally cultivated the fertile soils of the steppe and forest-steppe for agriculture. Forests are predicted to migrate northward in a warmer climate and are likely to be replaced by forest-steppe and steppe ecosystems. We analysed potential climate change impacts on agriculture in south/central Siberia, hypothesizing that agriculture in traditionally cold Siberia may benefit from warming. Current carbon (C) fluxes in agrosystems have also been analysed, as they are important for the development of land use strategies. Potentials for cropping were evaluated based on simple climate indices such as temperature sums above a base of 5 °C (GDD5), and an annual moisture index (AMI), which is the ratio of GDD5 to annual precipitation. Envelope models which determine crop range, and regression models which determine crop yields, were constructed and applied to climate change scenarios for several time frames: 1960–1990, using historic data; and data taken from HadCM3 B1 and A2 scenarios for 2020 and 2090. Analyses of carbon fluxes in agrosystems showed that plant phytomass and soil humus serve as a principal C sink. Mineralization flux forms from phytodetritus decomposition, and recently formed humus includes portions of “used” mobile humus. Currently, the C balance of agrosystems is slightly in deficit: the C loss is 0.25 t ha−1 year−1. From 50 to 85 % of central Siberia is predicted to be climatically suitable for agriculture by the end of the century, and only soil potential would limit crop advance and expansion to the north. Crop production could double. Future Siberian climatic resources could provide the potential for a great variety of crops to grow which previously did not exist on these lands. Traditional Siberian crops could gradually shift as far as 500 km northward (about 50–70 km per decade) if soil conditions are suitable, and new crops which are non-existent today may be introduced in the dry south, which would necessitate irrigation. Agriculture in central Siberia would likely benefit from climate warming. Adaptation measures would sustain and promote food security in a warmer Siberia.

Significant Siberian Vegetation Change is Inevitably Brought on by the Changing Climate

The redistribution of terrestrial ecosystems and individual species is predicted to be profound under Global Climate Model simulations. We modeled the progression of potential vegetation and forest types in Siberia by the end of the twenty-first century by coupling large-scale bioclimatic models of vegetation zones and major conifer species with climatic variables and permafrost using the B1 and A2 Hadley Centre HadCM3 climate change scenarios. In the projected warmer and dryer climate, Siberian taiga forests are predicted to dramatically decrease and shift to the northeast, and forest–steppe, steppe, and novel temperate broadleaf forests are predicted to dominate most of Siberia by 2090. The permafrost should not retreat sufficiently to provide favorable habitats for dark (Pinus sibiric, Abies sibirica, and Picea obovata) taiga, and the permafrost-tolerant L. dahurica taiga should remain the dominant forest type in many current permafrost-lain areas. Water stress and fire-tolerant tree species (Pinus sylvestris and Larix spp.) should have an increased advantage over moisture-loving tree species (P. sibirica, A. sibirica, and P. obovata) in a new climate. Accumulated surface fuel loads due to increased tree mortality from drought, insects, and other factors, especially at the southern forest border and in the Siberian interior (Yakutia), together with an increase in severe fire weather, should also lead to increases in large, high-severity fires that are expected to facilitate vegetation progression toward a new equilibrium with the climate. Adaptation of the forest types and tree species to climate change in the south may be based on the genetic means of individual species and human willingness to aid migration, perhaps by seeding. Additionally, useful and viable crops could be established in agricultural lands instead of failing forests.