Global climate change and its impact on ecosystems

ISSN 2079�0961, Arid Ecosystems, 2014, Vol. 4, No. 3, pp. 135–141. © Pleiades Publishing, Ltd., 2014.Original Russian Text © A.I. Kulikov, L.L. Ubugunov, A.Ts. Mangataev, 2014, published in Aridnye Ekosistemy, 2014, Vol. 4, No. 3(60), pp. 5–14.

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INTRODUCTION

Global warming is a challenge to humankind. Thisfact is expressed in the United Nations FrameworkConvention on Climate Change (1992), whose firstlegal document was the famous Kyoto Protocol, issuedin 1997. Russia ratified it in 2004. Presently, intensivework on the problem is supervised by the Intergovern�mental Panel on Climate Change (IPCC). Climatechanges and the ecosystem responses to them areobserved everywhere, but they are of the greatestimportance in the Baikal region because of specificfeatures of that global natural heritage site and themagnitude of climatic and ecological processes occur�ring there.

MATERIALS AND METHODS

Climatic changes were assessed on the basis of thearchives of the Buryatian Center for Hydrometeorol�ogy and Environmental Surveillance (a branch of theTransbaikalian Board for Hydrometeorology andEnvironmental Surveillance) and data from Internetresources.

Trends in the changes were approximated by thelinear function Y = a + bX, where b is the slope coeffi�cient indicating the rate of parameter change. Thevariability of parameters was evaluated as the meansquare deviation (MSD) and the variation coefficient.The confidence of differences between samples waschecked by Student’s t test. Aridization indices weredetermined from Walter–Gossen climate charts.Regional desertification was analyzed on the basis ofthe archives of the Board of the Federal Real EstateCadaster Agency for the Republic of Buryatia.

RESULTS AND DISCUSSION

Climate aridization and the warming–aridization–desertification system. Warming caused variousadverse consequences: aridization, desertification,dehumification, permafrost degradation, carbon andoxygen sequestration disturbance, etc.

Although arid regions and deserts existed in formerclimatic epochs, ecosystems respond to current globalwarming by aridization and desertification. Thus, glo�bal warming formed new relationships or strengthenedthose formerly being latent. Now warming–aridiza�tion–desertification (WAD) is a triune system, thecomponents of which are closely interrelated. Climatefactors are the input, and the output is aridization anddesertification.

Global climate warming in the Northern Hemi�sphere is confirmed by long�term instrumental obser�vations made by weather stations of the World Meteo�rological Office and national offices. From 1860 to1998, global air warming was about 0.8°C. The meanincrease in air temperature in Russia since the begin�ning of the 20th century is estimated to be within 0.9–1.1°C (Anisimov et al., 2007). In some sites of north�ern Russia, air temperature has risen by 1.0–1.5°C inthe past 30–35 years. The most profound climatechanges occur in the temperate belt. Warming is mani�fested there by an air temperature increase of 1.6–2.1°C over the past 30–35 years.

Russia witnesses greater changes than the globe asa whole. Even greater changes occur in the Baikalregion (Kulikov et al., 2008). In the past 30–35 years,the air temperature increased by 3.6°C per decade andby 2.3°C/10 years since the beginning of the 20th cen�tury (Fig. 1). Faster warming in Cisbaikalia and Trans�baikalia is noted by other scientists as well.

Global Climate Change and Its Impact on EcosystemsA. I. Kulikov, L. L. Ubugunov, and A. Ts. Mangataev

Institute of General and Experimental Biology, Siberian Branch of the Russian Academy of Sciences,ul. Sakhyanovoi 6, Ulan�Ude, 670047 Russia

e�mail: kul�[email protected], [email protected] November 8, 2013

Abstract—The main parameters of global warming are considered. In the Baikal region, warming occursfaster than anywhere in Russia or in the world. Ecosystems respond to warming by aridization and desertifi�cation. Taking into account the close reciprocal relationships among these processes, one may regard warm�ing (W), aridization (A), and desertification (D) as an integer WAD system.

Keywords: climate, global change, aridization, desertification, permafrost

DOI: 10.1134/S2079096114030032

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KULIKOV et al.

In some sites of Buryatia, the annual air tempera�ture has risen above zero. This fact dramatically altersthermodynamic conditions. Processes occur at annualheat cycles within positive temperature ranges, andwater remains liquid for most of the annual cycle.Thus, the heat exchange for water/ice phase transi�tions decreases, and biochemical processes are accel�erated according to Vant–Hoff’s rule.

Response of ecosystems to climate changes. The lifeof biota and ecosystems closely depends on climate,and this dependence is evident from the zonal distri�bution of major biomes on the Earth. In turn, the biotasupports the equilibrium of the partial pressures of car�bon dioxide, water vapor, and other greenhouse gasesand thereby controls the radiation–heat balance.However, this negative feedback loop is increasinglydisrupted, and a positive feedback increases. Thus, theautoregulation of the climate–biota system is dis�turbed.

Steppe landscapes tend to be choleric. This meansthat ecologic processes and phenomena are particu�larly unstable in time and area, and any index, includ�ing MSD, can be a measure of this instability. Thecholeric temperament is evident from the broad varia�tion in precipitation in Transbaikalian steppes. Theprecipitation amplitude, i.e., the difference betweenthe maximum (617.3 mm in 1990) and minimum(176.4 mm in 1954) annual values, is beyond compar�ison: 441 mm. The MSD of annual precipitation in1935–1942 was ±32.2 mm, whereas present devia�tions from the mean are even greater, with the MSDbeing ±65–83 mm.

We compared the MSD for two time spans, 1961–1990 and 1979–2007, within 50–60°N from the east(Kluchi, 160.8°E) to the west (Chisinau, 28.9°E). Thisdirection, from Kyakhta to Chisinau, matches theVoeikov wind�dividing axis. This axis starts from thesteppe and desert Central Asian plains, where a pow�

erful high�pressure field forms in winters. The Sibe�rian anticyclone extends westwards through theBaraba–Kulunda steppe corridor to the northern Cas�pian and Volga regions and further to the Don steppesand Danube pusztas.

The data draw us to the conclusion that tempera�ture conditions become less stable with climate warm�ing throughout the whole axis from east to west. InBuryatia, steppes become even more choleric withwarming. The winter and summer MSDs show a statis�tically significant difference: tf = 5.4 > t = 3.5 (P > 0.99),and summers are increasingly unstable in heat supply.

From July to September, highly variable landscapesare 20–30% more variable in temperature and moist�ening than heavy permafrost soils. It is apparent whythe bioproductivity of both natural and industrial plantcenoses in dry steppes is unstable from year to year.

The high variability of steppes becomes even morepronounced in conditions of current aridization, andthis fact, in turn, further increases aridization; thus, wesee the action of reciprocal systemic links.

Aridization, as a consequence of warming in theregional climatic system, is also supported by a posi�tive feedback loop with a predominance of radiationalregulation of the surface temperature. Warmingimplies an increase in the number of unshadowed dayswith greater solar heating of the active surface, causingits desiccation, and the desiccation favors furtherheating of the surface. However, in our opinion, theactivation of the positive feedback is primarily drivenby ecosystemic causes. The warming and greater heat�ing of the active surface increases evaporation, andevaporation increases surface temperature, therebystimulating itself further. Nevertheless, the externalfactors of purely climatic nature should not be under�estimated. Such external factors of positive feedbackcan be reduced total precipitation, a lower frequencyof efficient precipitation (more than 5 mm/day), anda higher frequency of extremely low precipitation(especially droughts).

Climate warming is a fact that should be takenaccount in industry, in particular, in soil improvement.The empirical equation for Selyaninov’s hydrothermalindex (HTI) is Ev = Σt > 10°C/10, where Ev is waterevaporation, mm, and Σ is the sum of active air tem�peratures. According to this equation, the evaporationpotential for Buryatia, with the discovered growth ofthe sum of active temperatures by 370–450°C, hasincreased by 37–45 mm. It follows that, even now, irri�gation standards should be increased by 370–450 m3/hawith regard to evaporation deficiency.

One of the main signs of aridization is droughts,that is, the dramatic inconsistency between the watersupply to plants and water expenditure, which resultsfrom a prolonged absence or considerable reduction ofprecipitation (in comparison to long�term values),elevated air temperatures, and severe winds.

2

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r = 0.98 ± 0.08y1 = 0.0229x – 2.5572

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Fig. 1. Long�term dynamics and trends of mean annual airtemperature in Buryatia in 1900–2011s. Row 1, 1900–2001; Row 2, 1970–2011.


GLOBAL CLIMATE CHANGE AND ITS IMPACT ON ECOSYSTEMS 137

An exacerbation of droughts was detected in Bury�atia by the Walter–Gossen climate chart method, theadvantage of which is pictorial realism (Fig. 2). Beforethe development of desertification processes (until1960s), the drought season lasted for 54–59 days, andsince the beginning of desertification (since 1970s) ithas become longer by 13–18 days. It is of special inter�est that a segment illustrating autumn aridization, notrecorded earlier, appears on the curve. Probably, this isthe cause of the rise in the frequency of autumnal for�est fires in Transbaikalia.

Aridization is still going on. This particularly con�cerns air droughts. In the first decades of the time spanunder study, the duration of air drought was assessed tobe 16–24 days. At present, in spring air droughts lastfor 29 days, and in autumn, they last for 37 days. Thus,the bulk duration of dry seasons is 65 days. The num�ber of days with active temperatures above 10°C hasincreased by 20 in comparison to 1930–1960s.

Climate warming an increased aridity gave rise todesertification. The United Nations Convention toCombat Desertification, adopted in 1994 and adoptedby over 170 countries, including the Russian Federa�

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tion in 2003, defines desertification as “land degrada�tion in arid, semiarid and dry subhumid areas resultingfrom various factors, including climatic variations andhuman activities.” A method developed by the Foodand Agricultural Organization and the United NationsEnvironment Program (FAO/UNEP) has been pro�posed for the assessment and mapping of desertifica�tion processes. This method is generally accepted andused with minor modifications in many countries,including Russia.

Types, classes, and aspects of desertification arerecognized. Desertification types are types of landdegradation: water erosion, Aeolian erosion, salina�tion, crust formation, soil compaction, reduction oforganic matter in soil, presence of toxic substances,and vegetation degradation. It is recommended thatthe types be assessed according to four desertificationclasses: weak, moderate, heavy, and extreme. Deserti�fication aspects include: the present state (PS); thedesertification development rate or the velocity of theprocess (DR); intrinsic desertification hazard (IDH),depending in particular on the topography and illus�trating its stability with regard to degradation; theimpact of animals on the environment (AI), deter�mined by the number of grazing animals per unit area;and the population density (PD), determined as thenumber of people per 1 km2. The index of overalldesertification hazard (ODH) summarizes all deserti�fication aspects: ODH = PS + DR + IDH + AI + PD.

The contribution of each aspect is determined byempirical scoring. The criteria are regional. They mayinclude additional parameters.

It is the practice to differentiate climatic andanthropogenic desertification, although they are sel�dom found separately. Climatic desertification is theresult of regional aridization, together with the degra�dation of arid lands in a climatic system with positiveand negative precipitation–albedo feedback loops(Zolotokrylin, 2005). Arid, semiarid, and dry subhu�mid lands include regions (aside from Arctic and Sub�arctic regions) where the ratio between the meanannual precipitation and potential evapotranspirationvaries within 0.05–0.65 (United Nations Convention…,1994). Selyaninov’s HTI is included in the standardlist of aridity indices, probably as a result of simple cal�culation.

Anthropogenic desertification is caused by wastefuluse of lands. Two subregions with predominance of theanthropogenic desertification factor arose in the secondhalf of the 20th century in plain semiarid and subhumidregions of Russia. The European subregion covers657,900 km2, and the Asian covers 1,460,000 km2 (Kustet al., 2002). In the European subregion, the predom�inant anthropogenic desertification factor is vegeta�tion degradation caused by grazing, and in the Asiansubregion, it is supplemented by a loss of soil fertilitybecause of ploughing of virgin and fallow lands.

Studies in Buryatia revealed regional features ofdesertification. Kulikov (Subregional’naya pro�

gramma…, 2000) proposed that the new cryogenicdesertification type be added to the FAO/UNEP list.The scope and statistical features of desertification weredemonstrated, and risks were assessed (Ubugunov et al.,2011). There are all of the prerequisites for climaticdesertification of Buryatian steppes. With regard toglobal changes and anticipated arid�type warming, therisk of climatic desertification further increases.

Buryatian steppes constitute, on the one side, theeastern flank of the integer Eurasian desert–steppemassif and, on the other side, its northern margin. Thespecific geographic location caused specific desertifi�cation features. Desertification was and is closely syn�genetically linked to the periodic activation of sands,which has been caused by the severe periglacial cli�mate persisting throughout the Quaternary.

Almost one half of the 2,293,800 ha of farming landsexperience various types of desertification (Table 1).Degradation is the most profound in arable lands, ofwhich 76% are being desertified. Pastures and hay�lands occupy 1,475,100 ha, and bioproductivity falls in29% of them as a result of desertification.

Deflational soil degradation is the predominantcomponent of desertification. Water erosion also con�tributes much, especially on sandy loesses. Sheetwashing and gullying involve slopes at edges of mostintermontane depressions and piedmont diluvial andalluvial plains devoid of natural vegetation as a result ofploughing, forest fell, and overgrazing. Littered pineforests and steppes on sands and loess deposits are rap�idly degraded by industrial development. Theybecome unstable and disrupt ecological equilibrium.Such landscapes occur mainly in river drainage areas.

Soil dehumification is one of the consequences ofdesertification. We assume that up to 70% of thehumus store and associated energy have been lost. Pre�dictive humification models have been constructed.We calculate that the amount of feedstock energy inthe humosphere of the region is 1100 × 1014 kJ, and itsgross loss during desertification may be as large as 7 ×1010 kJ. Currently, carbon binding by photosynthesisexceeds its industrial emission, but desertification canshift this positive balance. The present humosphere ofthe region contains 3.1 × 109 tons of carbon, and dehu�mification has supplied an additional 2.2 × 109 tonsinto the atmosphere. By 2010, 20 × 106 tons more willbe released just from the chestnut soils of Buryatia.

Another source of greenhouse gases is the degrada�tion of the carbonate horizon in steppe and dry�steppesoils, which undergo the greatest desertification. Atpresent, 3.6 × 109 t CO2, or 9.82 × 108 t of carbon aredeposited in the form of carbonates in Buryatiansteppes. The future emission of carbonate carbon intothe atmosphere is predicted to be about 1.0 × 107 t C.

The permafrost zone is the most sensitive to ther�modynamic changes on the Earth, because its forma�tion and existence closely depend on the radiation–heat balance. It responds to warming with a reduction



of its geographic range, elevated temperature, anddeeper seasonal thawing (Fig. 3).

In 1909–2008, the seasonal thawing depthincreased to 1–1.6 m on open plain divides in Buryatia(Fig. 3, curves 2, 5, 7–9) and by about 0.2–0.5 m inforests (Fig. 3, curves 3, 6). Closed poorly draineddepressions show zero or negative trends (Fig. 3,curves 1, 4). The temperature rise at the referencedepth (1.6 m) is 0.05–0.08°C/year, and at some sitesthe mean annual temperature rises above zero; thus,permafrost restoration becomes impossible. Buryatiastands out among other regions in the fastest perma�frost thawing.

Predictions of climate changes and ecosystemresponses. The accelerated warming is caused mainlyby increasing concentrations of so�called greenhousegases: water vapor, CO2, CH4, N2O, tropospheric O3,anthropogenic halocarbons, and others listed in theMontreal Protocol on Substances That Deplete theOzone Layer (1988). Majority of them are long�living:CO2, 100 years; N2O, 120 years; and some minor com�ponents, 10–50 kyr.

The most recent climate models based on generalcirculation of the atmosphere and climate (GCMs)show that both arid and humid warmings may happenin the 21st century. It is expected that in Buryatia Σt ≥10°C will tend to increase by 94°C/10 years on average,and July temperatures will increase by 0.6°C/10 years.The results will include decreasing humidity andhydrothermal factors, accelerated humus oxidation insoils, and a decreasing yield of spring cereal crops. Theincreasing aridity is confirmed by adverse trends in theyields of cereals in Buryatia, Irkutsk oblast, andZabaikalskii Krai.

A bioclimatic model of Siberian vegetation (Che�bakova et al., 2003) shows that the equilibrium vegeta�tion in 2090 will be characterized by a twofold reduc�tion of forest areas and the same increase in the area ofdesertified steppes in the case of the arid warming sce�nario. The steppe border will shift north by 10°, andsteppe areas will increase by 30%. These processes will

lead to a loss of vegetation diversity, especially in areasexperiencing desertification.

Carbon sequestration will change dramatically. Atpresent, the carbon balance in Russian soils is positive,but the amount of carbon deposition in species resis�tant to thermodynamic settings; that is, humus, is low,0.05 Gt/year (Zavarzin, 2001). The store of soilorganic matter in Russia at the end of the 20th centurywas 300 Gt (Orlov et al., 1996). The supply with litterfall was 4.4 Gt/year, and emission with respiration was4.3 Gt/year.

It is expected that warming will cause dehumifica�tion of steppe soils and, in contrast, increased humifi�cation in forests lacking heat. In permafrost soils, theice content will decrease, and humification will notonly increase but result in profound changes withincreased proportions of the condensed humin com�

Table 1. Desertification of farming lands in the Republic of Buryatia (1000 ha)

Desertification types Farming landsOf them

arable lands haylands pasturelands

Deflational 338.8 239.5 5.5 93.8

Water�erosional 237.4 170.2 3.6 63.6

Mixed: deflation + erosion 177.2 124.5 3.2 49.5

Halogeochemical 172.5 23.6 44.9 104.0

Modification–salination 23.1 10.5 2.3 10.3

Hydromorphic 171.4 9.2 48.6 113.6

Total 1120.4/48.8* 577.5/76.0** 108.1 434.8

* As a percentage of the areas of all farming lands, which total 2293800 ha. ** As a percentage of all arable lands, which total 759900 ha.

1.01909 1981 2008

1.5

2.0

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Years

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8

9

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KULIKOV et al.

plex in the humus. However, intense degradation oforganogenic horizons (steppe mat, forest litter, andthe peat layer) is quite probable. It may launch a posi�tive feedback loop, favoring further degradation ofpermafrost rocks.

During warming in Buryatia, mean annual temper�atures have already become positive in many sites,thereby hampering permafrost conservation. The areaof permafrost degradation is expected to expand fur�ther. Permafrost temperature is predicted to rise byabout 1.5–2°C, and the depth of seasonal thawing willincrease by 25–50%. Calculations based on Kudryav�tsev’s model (Obshchee merzlotovedenie…, 1978) showthat with invariable thermodynamic properties (ther�mal conductivity λ = 4.48 kJ/(m h °C, heat capacityC = 2095 kJ/m3°C, and heat input for soil thawingQf = 98884 kJ/m3) and constant temperature ampli�tudes, a temperature rise to 0°C will deepen thawing to3.8 m. Starting from that time, the seasonal thawinglayer will be so thick that it will not freeze in full withinthe cold season. The upper portion of the permafrostlayer will remain constantly unfrozen. It will be separatedfrom the surface and be converted to a relict, and perma�frost soils will become seasonally frozen (Table 2).

Permafrost degradation can disrupt the carboncycle. The amount of soil carbon deposited in perma�frost zones throughout the globe is estimated to be455 Gt, or 14% of the whole soil carbon. The carbonbalance is close to zero, and the soil functions of netdrainage and its source vary with seasons and fromyear to year. The increase in temperature and soilthawing depth, particularly, in bog cryogenic soils,may shift the balance significantly and make the per�mafrost zone an emitter of greenhouse gases. It shouldalso be mentioned that larch forests of northeasternEurasia constitute 30–40% of the world area of coniferforests and fix about 480 ± 200 Mt C/year, whereascarbon emission from soils and forests at high latitudesis 290 Mt C/year, soils contributing over 70%.

Russia possesses huge areas of boreal forests andpermafrost soils, which are objects of net drain in Eur�asia. Since Canada has become a country emittinggreenhouse gases, Russia has remained the sole globalcenter of ecological stabilization.

CONCLUSIONS

Climate warming occurs in the Baikal region fasterthan anywhere else in Russia or on the Earth. This isconfirmed by increasing mean annual air tempera�tures, especially in the last 30–35 years. Warmingcauses a number of adverse ecosystemic changes,including further aridization determined by elevatedevaporation. Aridization, in turn, increases the fre�quency of droughts, and autumnal droughts, notobserved earlier, are recorded now. Aridization is wors�ened by the choleric temperament of steppes, that is,the especial instability of ecologic processes. This phe�nomenon manifests itself in the broad variability ofannual precipitations. The difference between theirmaximum and minimum values is enormous. Warm�ing increases the mean square deviation of annual pre�cipitation. The areal increase in cholericity is demon�strated by the elevated air temperature variation alongVoeikov’s axis for two time spans.

Another response of ecosystems to warming isdesertification. The current and predicted conditionsin the Baikal region favor climatic desertification.With regard to the wide area of permafrost, a specialtype of cryogenic desertification is proposed. Perma�frost responds to warming by increasing seasonalthawing, which causes a number of adverse conse�quences. In the future, permafrost soils may evolve tobe seasonally frozen.

REFERENCES

Anisimov, O.A., Lobanov, V.A., and Reneva, S.A., Analysisof changes in air temperature in Russia and empiricalforecast for the first quarter of the 21st century, Russ.Meteorol. Hydrol., 2007, vol. 32, no. 10, pp. 620–626.

Chebakova, N.M., Reindeldt, G., and Parfenova, E.I.,Redistribution of vegetation zones and populations ofSiberian larch and Scots pine at the climate warming,Sib. Ekol. Zh., 2003, no. 6, pp. 677–686.

Kust, G.S., Glazovskii, N.F., Andreeva, V.A., Shevchenko, B.P.,and Dobrynin, D.V., General results of assessment andmapping of desertification in Russian Federation, Arid.Ekosist., 2002, vol. 8, no. 16, pp. 7–27.

Table 2. Prediction of seasonal thawing depth changes with climate warming

Physical amplitude of temperature on soil surface (A0, °C) Mean annual soil temperature, (t0, °C) Soil thawing depth (h, m)

15* –3* 2.6*

–2 3.0

–1 3.4

0 3.8

* At present.



Obshchee merzlotovedenie (geokrinologiya) (FundamentalPerfrostology (Geocryology)), Kudryavtsev, V.A., Ed.,Moscow: Mosk. Gos. Univ., 1978.

Orlov, D.S., Biryukova, O.N., and Sukhanova, N.I., Organ�icheskoe veshchestvo pochv Rossiiskoi Federatsii (SoilOrganic Matter in Russian Federation), Moscow:Nauka, 1996.

Subregional’naya programma po bor’be s opustynivanie dlyaRespubliki Buryatiya, Aginskogo Buryatskogo avtonom�nogo okruga i Chitinskoi oblasti (Subregional Program toCombat Desertification in Republic of Buryatia, Agin�skii Buryat Autonomous District, and Chita Oblast),Ulan�Ude: Buryat. Nauchn. Tsentra, Sib. Otd., Ross.Akad. Nauk, 2000.

Ubugunov, L.L., Kulikov, A.I., and Kulikov, M.A., On theapplication of risk analysis technology for assessment ofthe ecological hazard of desertification (by the example

of Republic of Buryatia), Contemp. Probl. Ecol., 2011,vol. 4, no. 2, pp. 178–185.

United Nations Convention to Combat Desertification inThose Countries Experiencing Serious Drought and/orDesertification, Particularly in Africa (UNCCD), Paris,1994.

Zavarzin, G.A., The role of biota in global climate change,Russ. J. Plant Physiol., 2001, vol. 48, no. 2, pp. 265–272.

Zolotokrylin, A.N., Monitoring of climate factors affectingdesertification, in Problemy ekologicheskogo monitor�inga i modelirovaniya ekosistem (Problems of Environ�mental Monitoring and Simulation of Ecosystems),Izrael’, Yu.A., Ed., St. Petersburg, 2005, vol. 20,pp. 105–123.

Translated by V. Gulevich

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Global climate change and its impact on ecosystems