Annals of Arid Zone 47(3&4): 457-471, 2008

Climate Change and Urbanization in Arid Regions

Boris A. portnov1 and Shlomit paiI Department of Natural Resources and Environmental Management, Graduate School of

Management, University of Haifa, Haifa, IsraelZ Department of Geography and Environmental Studies, University of Haifa, Haifa, Israel

Abstract: Ongoing global climate change, which manifests itself in the greaterinter-annual variability of precipitation, rising summer temperatures, and increasingperiods of droughts, is likely to affect the pace of arid land urbanization in threedistinct ways: (a) increasing migration of desert nomads into urban areas; (b)restructuring of regional economies towards reducing the relative share of traditionalwater-intensive agriculture, and (c) increasing the number of urban settlements inarid regions due to expansion of deserts towards arid land fringes. The presentpaper looks into the interaction between the climate change and urbanization inarid regions and formulates recommendations for urban and regional developmentpolicy aimed at a more sustained urban growth in arid regions.

Key words: Deserts, arid zones. urbanization. climate change.

The Earth's climate is mainly influencedby the solar energy, but also by the amountof greenhouse gases and aerosols in theatmosphere (O'Hare et al., 2005). Theconcentrations of greenhouse gases suchas carbon dioxide (COz), methane (CH4)and nitrous oxide (NzO) in the atmospheresignificantly increased since the beginningof the Industrial Revolution, mostly as aresult of human activities, such as fossilfuels burning, biomass utilization anddeforestation (Houghton, 2004). Theburning of fossil fuels has also resultedin emissions of aerosols that absorb andemit heat, and reflect light. These additionsof greenhouse gases and aerosols havechanged the composition of the atmosphereand led to climatic changes that influencetemperature, precipitation, winds and sealevel on global and regional scales (EPA,2007). It seems that climate changeprocesses are already happening, being one

of the greatest environmental, social andeconomic threats facing the planet (IPCC,2007a; ED Environment, 2008). Accordingto the prediction results of various globalclimate models (see inter alia Wigley andRaper, 2001; Stott and Kettleborough, 2002;Knutti et al., 2003; Furrer et al., 2007),without further actions to reduce green-house gas emissions, the global averagesurface temperatures are likely to rise bya further 1.8 to 4.0°C by the end of thiscentury, and by up to 6.4°C in the worstcase scenano.

Climate change affects human systemsIn three principal ways: first, it providesa context for climate-sensitive humanactivities, such as water shortage forirrigation. Second, it affects the cost ofmaintaining climate-controlled environm-ents for human life and activity, and, third,it interacts with other types of stresses onhuman systems, such as rural-urban

458 PORTNOV & PAZ

migration as a result of drought. In mostcases. climate change exacerbates the stressthat human activity imposes on the naturalenvironment (IPCC, 2007a).

Rapid urbanization in arid regions,especially susceptive to climate change, isa special concern, because it concentratespeople and economic assets inenvironmentally high-risk areas and thusincreases global and regional vulnerabilityto climate change impacts (Scott et al.,200 I). Urban area in developing countriesis a good example of this impact, wherelow capacity drinking water systems areunable to deal with periodic droughts andincreased evaporation as a result of climatewarming, concomitant with rapid populationgrowth (IPCC, 2007b).

Today, more than a half of the worldpopulation lives in urban centers, dependingon industry, services and infrastructures forpersonal income, well-being and day-to-daymobility (UN, 2006). According to the UN'srecent estimates, major population growthin the next decades will take place in urbanareas, mostly in medium-size cities of Ito 5 million residents (or even in smallercities of less than 500,000 people). Themajority of these cities are located in thedeveloping countries, especially in Asia andAfrica, a sizable part of which are classifiedas arid and semi-arid countries (UN-Habitat,2003; IPCC, 2007b).

The present paper looks into theinteraction between the climate change andurbanization in arid regions. It starts witha brief review of climate changes on theglobal scale and in different regions ofthe world, especially those susceptive toaridity. The analysis is followed by a briefreview of potential trends in urban

development patterns attributed to bothongoing and potentially forthcoming climatechange. In particular, we discuss populationmovements to and within arid regions andtheir interaction with the urban environment.Two types of population movements intoarid regions are evident today: migrationinto permanent settlements (urbanization)and short-term visits (tourism); bothurbanization and short-term migrationincrease the pace of population growth inthe arid zones. Recommendations for urbanand regional development policy concludethe discussion.

Climate Change Impacts on AridRegions

Arid regions and their climaticcharacteristics

Arid regions are one of the largestterrestrial biomes, where the potentialevaporation ratio exceeds the amount ofprecipitation (Nicholson, 2002; Warner,2004; Smithson et al., 2002). Their typesrange between regions with sufficientmoisture (semi-arid, semi-desert regions),where the precipitation is around 300 mmper year, to hyper-arid regions (extremedeserts), where the rainfall is 50 mm peryear or even less (Nicholson, 2002; Warner,2004; Reid et al., 2005).

The core areas of the dry lands are thesubtropical high-pressure systems. Sinkingair from high altitudes, as a part of theHadley cell, tends to warm and dry duringus subsiding, which minimizes the chanceof rainfall (as in the Sahara desert). Mountainranges may also play a role, causing a"rain shadow" on their lee side. For instance,in Asia, the great Himalayan chain prevents

CLIMATE CHANGE AND URBANIZATION 459

the summer monsoon flow of the IndianOcean air from reaching the interior. Othernatural factors causing aridity are largedistance from water source (one well-knownexample is the Gobi deselt) and the locationnear a cold ocean current (e.g. Peruviancoasts) (Smithson et at., 2002).

Due to their low agriculturalproductivity, the deserts support no morethat 10 people per km2

, with the lowestpopulation density across all eco-regionsf the world (Reid et at., 2005).

Drought

Drought, commonly associated witharidity, is a complex, multifacetedphenomenon which is difficult to defineprecisely. According to O'Hare et at. (2005)and Heim (2002), it is a prolonged periodof abnormally dry weather, which causesa serious hydrological imbalance. It hasnumber of facets: "meteorological drought,"which is mainly a prolonged deficit ofprecipitation; "hydrological drought," whichis related to below-normal stream flow,lake and groundwater levels, and"agricultural drought" that relates tomoisture deficits in the topmost layer ofsoil (the root zone) that impacts crops (ibid).Droughts occur in most countries, in bothdry and humid regions alike, and their spatialextent and severity vary on seasonal andannual timescales (WMO, 2006). Followingthe Palmer Severity Drought Index-PSDI(Palmer, 1965; Heim, 2002), evapotran-spiration and drying are important factorsthat contribute to droughts. Climatic modelspredict that drought processes areencouraged by an increase in temperaturesassociated with a decrease in precipitation(lPCC, 2007a).

Desertification

The transition zones surrounding desertshave very fragile, delicately balancedecosystems. In these marginal areas, humanactivities may stress the ecosystem beyondits tolerance (or carrying capacity) limits.By pounding the soil with their hooves,livestock compact the substrate, increase theproportion of fine material, and reduce thepercolation rate of the soil, thus encouragingerosion by wind and water. Grazing andthe collection of firewood reduce or eliminateplants that help to bind the soil. The resultis degradation of the land, causingdesertification, which leads to the expansionof deselt-like conditions into non-deselt area(USGS, 1997; Tarbuck and Lutgens, 2005).Recent studies estimate that between 10-20%of the dry lands are degraded because ofhuman intervention, creating an imbalancebetween demand and supply of ecosystemservices. These critical services include waterfor humans and livestock, water for sanitationand irrigation, fuel, building materials, wildfood sources, forage and grazing, and geneticresources, particularly of arid-adapted species(Adeel et at., 2005; Hassan et at., 2005).

Desertification is a global phenomenonthat is spurred by climate variations,especially by drought (Houghton, 2004;O'hare et at., 2005). The progress ofdesettification in drylands is likely to increasein the next decades due to more frequentand intense droughts, as a result of expectedclimate change (Houghton, 2004).

Global climate change impacts onarid regions

Global climate change is likely to affectarid regions in several ways. Accordingto IPCC (2007b), theses influences, together

466

PROS:

Unique mineralresources

Healthy climate

Abundant land

Low demand - lowland cost

+

PORTNOY & PAZ

EXOGENOUS FACTORS

CONS:

Remoteness

Isolation

Harsh environmentalconditions

Lack of previousdevelopment

+• Growing shortage of landfor development in coreareas (specifically forterritory consumingenterprises)

• Exhaustion of mineralresources in non-desertregions

• New knowledge aboutdesert climate and its effecton human health

• Improvement in themeans of transportation

• Possibilities of localproduction of freshwater and itstransportation fromexternal sources;

• Network technology andtelecommunication

• Climate change

Fig. 2. Factors affecting urbanization in desert regions (after: PorlllOV andSafriel, 2004)

L

resources are concemed. The "low-resource" societies will thus requiresubstantial exogenous aid to achieve theeconomy-transformation goal or willotherwise sink even deeper into the viciouscircle of famine and poverty.

The expected global warming may alsoaccelerate the pace of desertification orthe process of geographic expansion ofdeserts, which is already evident today(Middleton and Thomas, 1997). This processwill draw the desert frontier closer to manyexisting population centers, located todayin semi-arid zones, thus bringing more citiescurrently located in desert fringes closer

to the desert; some of them will becomedesert cities eventually. Thus, as a resultof climate change more non-desert peopleof today are likely to become desert dwellersof tomorrow, not by their own free choice,but by the merciless forces of nature.

Conclusions

Two major factors hamper theattractiveness of desert settlements fornewcomers limited employmentopportunities and remoteness from majorcities outside desert regions, which are majornational foci of employment, services andcultural life. However, if these drawbacks

CLIMATE CHANGE AND URBANIZATION

4,000,000

467

::l! 1,000,000 1 x500,000 1-. ----'X/

X-X---o 1;( 'It. )(( '1. l1C

1890 1900 1910 1920 1930

1,500,000

3,500,000

!!lc:: 3,000,000<l>

"Ul 2,500,000~c:: 2,000,000o

~

___X_I

X=X x-----='x 1"-......X_X~

~

- x-x~ ',( ),( t~:~.~ .....

1940 1950 1960 1970 1980 1990 2000 2004

Year

--i>-Phoenix, AZ -*-Tucson, AZ _x_Detroit, MI _Chicago, IL

Fig. 3. Comparative trends of population growth of selected cities in theUnited States (Source: Assembled from publications of the US CensusBureau)

are mitigated (e.g., as in Tucson andPhoenix, AZ), desert cities may exhibitimpressive growth, outranking evenlong-established non-desert communities(Fig. 3). Although successful desert citiessuch as Tucson and Phoenix are ratherunique cases, their success factors (thatis, the combination of infrastructuredevelopment and employment creation) maybe emulated in other desert areas, thusleading to more sustained urbanizationtrends in the arid zones.

Achieving this goal will, however, requirea major change in the existing regionaldevelopment paradigm.

In our view, a main reason for the failureof regional policy to achieve a desirableinterregional population shift towards urbanareas in arid zones is the so called"compensatory approach" to selectingdevelopment incentives. For instance,regional policy makers may try to compensate

relative disadvantages of arid regions (e.g.,a lack of previous urban development, harshenvironment, inferior infrastructure andcommunication networks) by tax benefitsor more affordable public housing. Thesemeasures may, however, have only a limitedeffect on the interregional population change.

In contrast, the "counter-balanced"approach we advocate assumes that relativedisadvantages of peripheral regions shouldbe counter-balanced rather than compensated(Portnov and Etzion, 2000). For instance,a lack of previous urban dev~lopment ina peripheral arid region can be reduced bycreating dense urban clusters in which smallurban settlements share some essential urbanfunctions - employment, educational, culturaland recreational services and facilities - whereeach of the small localities cannot individuallysustain (POItnov and Safriel, 2004).

In order to diversify the employmentbase of peripheral areas, another strategy

PORTNOY & PAZ

- the strategy of redirecting prioritIes -can also be employed. Such a strategyassumes that development resources shouldbe primarily concentrated on a limitednumber of selected urban communities inthe frontier areas (Portnov and Erell, 1998).This should be done until these communitiesbecome sufficiently attractive to bothmigrants and private developers. Suchsupport can then be redirected, on a stage-by-stage basis, to other frontier settlements.Combined with traditional compensatorypolicy mcasures (provision of publichousing, tax incentives, etc.), theaforcmentioned development strategies mayimprove substantially the quality of urbanlife in arid regions by attracting moremigrants and private developers there.

References

Ahu- Taleh. M.F. 2000. Impacts of global climatechange scenarios on water supply and demandin Jordan. Water IllIemational 25: 457-463.

Adeel, Z., Safriel, U., Niemeijer, Doo White, R ..de Kalbermatten, Goo Glantz, M., Salem, B.,Scholes, R., Niamir-Fuller, M., Ehui, S. andYapi-Gnaore. V. (Eds.) 2005. Ecosystems andHuman Well-being: Desertification Sylllhesis.Island Press. Washington. District of Columbia,36 pp.

Alpert. P .. Ben-Gai. T.. Bahrahad. A., Benjamini,Y .. Yekutieli. D .. Colacino. M., Diodato, L.,Ramis. c., Homar. V .. Romero, R .. Michaelides,S. and Manes. A. 2002. The paradoxical increaseof Mediterranean extreme daily rainfall in spiteof decrease in IOtal values. Geophysical ResearchLellers 29(11): doi: 10.1029/200 IGLOl3554

Barlow, M., Cullen. H. and Lyon. B. 2002. Droughtin central and southwest Asia: La Nina, thewarm pool, and Indian Ocean precipitation.Journal of Climate 15: 697-700.

Biggs. R .. Bohensky. E.. Desanker, P.V .. Fabricius,C .. Lynam, T., Misselhorn. A.A., Musvoto, C ..Mutale, M., Reyers, B .. Scholes, R.J., Shikongo.S .. and van Jaarsveld, A.S. 2004. NalllreSupporting People: The SOlllhem African

Millennium Ecosystem Assessmelll IntegratedReport. Millennium Ecosystem Assessment.Council for Scientific and Industrial Research,Pretoria, 68 pp.

Bou-Zeid. E. and EI-Fadel, M. 2002. Climate changeand water resources in Lebanon and the MiddleEast. Journal of Water Research Planning alldManagemelll 128: 343-355.

Burke, E.J., Brown. S.J. and Christidis, N. 2006.Modelling the recent evolution of global droughtand projections for the 21 st century with theHadley Centre climate model. Joumal ofHydrometeorology 7: 113-125

Confalonieri, U. 2003. Variabilidade climatica.vulnerabilidade social e saude no Brasil. TerraLivre, San Paulo, 19-1. 20. 193-204.

Dai, A., Lamb. Trenberth, P.J., Hulme, K.E., Jones,M., Pingping Xie, P.D. 2004. The recent Saheldrought is real. Intemational Journal ofClimatology 24: 1323-1331.

D' Hont, O. 1989. The population of the squatterdistricts of Nouakchott, or ·Kebe·. Mauritania,Cahiers d'Olllre Mer 42(165): 73-96.

Divon H. and Abou Hadab F. 1996 CollaborativeAgricultural and Rural Development ofSettlement in the Nubariya Region, Egypt(http://www jewish vi rtuall ibrary .org/j source/Peace/egmashav.html)

Duraiappah, A., Naeem, S .. Agardi, T., Ash. N ..Cooper, D .. Diaz, S .. Faith, D.P .. Mace. GooMcNeilly, J.A .. Mooney, H.A .. Oteng- Yeboah.A.A., Pereira, H.M., Polasky, Soo Prip. C .. Reid,W.V .. Samper, c., Schei. P.J .. Scholes. R ..Schutyser. F. and van Jaarsveld, A. (Eds.) 2005.Ecosystems and HlI1nanWell-being: BiodiversitySynthesis. Island Press, Washington, District ofColumbia, 100 pp.

ECA (Economic Commission for Africa) 2005.Assessing sustainable development in Africa.Africa's Sustainable Development Bulletin.Economic Commission for Africa, Addis Ababa,59 pp.

ECF (European Climate Forum) and Potsdam Institute2004. What is dangerous climate change? InitialResults of a Symposium on Key VulnerableRegions, Climate Change and Article 2 of theUNFCCC, Buenos Aires. Beijing, 39 pp.Available: http://www.european-climate-forum. net!.

CLIMATE CHANGE AND URBANIZATION 469

EEA 2004. Impacts of Europe's Changing Climate:An Indicator-Based Assessment. EEA ReportNo 2/2004, European Environment Agency,Copenhagen (or: Luxembourg, Office forOfficial Publications of the EC), 107 pp.

EPA 2007. Climate change. Available: http://www.epa.gov /cl imatechange/index. html

EU environment, 2008. Climate change. Available:http://ec.europa.eu/en viron mentlcli matlhomc_en.htm

FAa 2004. Seguridad alimentaria como estrategiade Desarrollo rural. Proc. 28ava ConferenciaRegional de la FAD para America Latina y1'1 CaribI'. Ciudad de Guatemala, Guatemala.

Furrer, R., Sain, S.R., Nychka, D. and Meehl. G.A.2007. Multivariate Bayesian analysis ofatmosphere-ocean general circulation models.Environmental and Ecological Statistics 14:249-266.

Golany. G. 1978. Planning urban sites in arid zones:The basic considerations. In Urban Planningfor Arid Zones (Ed. G. Golany), pp. 3-21. JohnWiley & Sons, New York.

Gonzalez, P. 2001. Desertification and a shift offorest species in the Wcst African Sahel. ClimateResearch 17: 217-228.

Hardy. J.T. 2003. Climate Change Causes, Effectsand Solutions. Wiley, Chichester, 247 pp.

Hassan, R., Scholes, R. and Ash, N. (Eds.) 2005.Ecosystems and Human Wellbeing: Volume I:CUITent State and Trends. Island Press,Washington, District of Columbia, 917 p.

Heim. R.R. 2002. A review of twentieth-centurydrought indices used in the United States. Bulletinof the American Meteorological Society 83:1149-1165.

Houghton, J. 2004. Global Warming. 3rd edition.Cambridge University Press, 351 pp.

ICBS 2005. Statistical Abstract of Israel #55. IsraelCentral Bureau of Statistics, Jerusalem.

IPCC 2007a. Working Group I Report - The PhysicalScience Basis. Available: http://www.ipcc.ch/ipccreports/ar4-wg I.htm

IPCC 2007b. Working Group II Report - Impacts.Adaptation and Vulnerability. Available:http://www.ipcc.ch/ipccreports/ar4-wg2.htm

Issar. A. 1999. 'The Past as a Key for the Futurein Resettling the Desert', in B.A. Portnov andA.P. Hare, Desert Regions: Population,

Migration, and Environment, Springer Verlag,Heidelberg, pp. 241-248.

Johansen, RJ. 200\. Impacts of fire on biologicalsoil crusts. Biological Soil Cmsts: Stmcture,Function, and Management (Eds. J. Belnap andO.L. Lange), pp. 386-397. Springer, Berlin.

Kates, R.W., Johnson, D.L. and Johnson-Haring,K. 1977. Population, Society and Desertification,in Desertification: Its Causes and Consequences.Pergamon Press, Oxford, pp. 261-318.

Knutti, R., Stocker, T.F., Joos, F. and Plattner, G.-K.2003. Probabilistic climate change projectionsusing neural networks. Climate Dynamics 21:257-272.

Lauenroth, W.K., Epstein, H.E., Paruelo, J.M., Burke,I.e., Aguiar, M.R. and Sala, O.E. 2004. Potentialeffects of climate change on the temperate zonesof North and South America. Revista Chilenade Historia Nalllral 77: 439-453.

Lin, E.D., Xu, Y.L., Ju, H. and Xiong. W. 2004.Possible adaptation dccisions from investigatingthe impacts of future climate change on foodand water supply in China. Paper presentedat the 2ndAIACC Regional Workshop for Asiaand the Pacific, 2-5 November 2004, Manila,Philippines. Available: http://www.aiaccproject.org/meeti ngs/Mani la_04/Day2/erda_nov3 .doc.

Lioubimtseva, E. and Adams, J.M. 2004. Possibleimplications of increased carbon dioxide levelsand climate change for desert ecosystems.Environmental Management 33: S388-S404.

Malheiros, 1.0.2004. 17 puntos que ajudam a explicaro que e la desertifica~1io, a conven~1io da ONUe 0 processo de constru~ao do PAN-LCDBrasileiro. RIOD BRASIL, II pp.

McLeman, R. and Smit, B. 2005. Assessing the securityimplications of climate change-related migration.Preprint, Human Security and Climate Change:An International Workshop, Oslo, 20 pp.

Middleton, N. and Thomas, D. (Eds.) 1997. WorldAtlas of Desertification. Arnolc1, London.

Morrow A. Tourism in Egypt still booming despitemilitant attacks (http://www.dawn.com/2005/05/0 Ilint 13.htm)

Mutangadura, G., Ivens, S. and Donkor, S.M. 2005.Assessing the progress made by southern Africain implementing the MDG target on drinkingwater and sanitation. Assessing sustainabledevelopment in Africa. Africa's Sustainable

470 PORTNOY & PAZ

Development Bulletin. Economic Commissionfor Africa, Addis Ababa. 19-23.

Myers, N. 2002. Environmental refugees: a growingphenomenon of the 21st century. PhilosophicalTrallSaClions of lhe Royal Academy of London,Series B - Biological Sciences 357: 609-613.

Niasse. M.. Afouda. A. and Amani, A. (Eds.) 2004.Reducing West Africa?s Vulnerability to ClimateImpacts on Water Resources, Wetlands andDesertification: Elements for a Regional Strategyfor Preparedness and Adaptation. InternationalUnion for Conservation of Nature and Resources(IUCN). Cambridge, 84 pp.

Nicholson. S.E. 2002. What are the key componentsof climate as a driver of desertification? GlobalOeserlificalion: Do Humans Cause Oeserls?(Eds. 1.F. Reynolds and D.M. Stafford-Smith),pp. 41-57. Dahlem University Press. Berlin.

O'hare. G., Sweeny. J. and Wilby, R. 2005. Wearher,C1inwle and Climale Change HumanPerspeclil'es, Pearson Educalion Limil. London,403 pp.

Oropeza, O. 2004. Evaluacion de la vulnerabilidada la desertificacion. Cambio Climatico: UnaVision Desde Mexico, J.Martfnez andA.Fernandez Bremauntz. Eds., SEMARNA T eINE. Mexico. 301-3 I I.

Palmer. W.e. 1965. Meteorological Drought.Research Paper 45. US Department ofCommerce. Weather Bureau, Washington, DC,58 pp. [Available from NOAA Library andInformation Services Division, Washington, DC20852.]

Paz. S.. Toun·e. Y. and Planton. S. 2003. NorthAfrica-West Asia (NA WA) Sea-Level PressurePatterns and its Linkages with the Easte11lMediterranean (EM) Climate. GeophysicalResearch Letters, 30(19): 1999-2002, doi:10. I029/2003GLO 1786.

Paz, S., Tourre, Y.M. and Brolley. J. 2008.Multi-temporal Climate Variability over theAtlantic Ocean and Eurasia: Linkages withMediterranean and West African Climate.Atmospheric Science Letters, DOl:10. I002/asl. 181.

Pedersen. 1. 1995 Drought, migration and populationgrowth in the Sahel: The case of the MalianGourma: 1900-1991. Popular ion Sll/dies 49(1),pp. 111-126.

Portnov B.A. and Safriel, U. 2004. Combatingdesertification in the Negev: dryland agriculturevs. dryland urbanization. Journal of AridEnl'ironmellls 56(4): 659-680.

Portnov, B.A. and Erell, E. 1998. Long-termDevelopment Peculiarities of Peripheral DesertSettlements: The Case of Israel. JlllernarionalJournal of Urban and Regional Research 22(2):216-32.

Prospero. J.M. and Lamb. P.J. 2003. African droughtsand dust transport to the Caribbean: climatechange implications. Science 302: 1024-1027.

Ragab. R. and Prudhomme. e. 2002. Climate changeand water resources management in arid andsemi-arid regions: prospective and challengesfor the 2151 century. Biosyslems Engineering81: 3-34.

Reason, C.J.e. and Keibel. A.2004. Tropical cycloneEline and its unusual penetration and impactsover the southern African mainland. WealherForecaSI 19: 789-805.

Reich, P.F., Numbem, ST, Almaraz. R.A. andEswaran. H. 2001. Land resource stresses anddesertification in Africa. Agro-Science 2: 1-10.

Reid, W.V., Mooney. H.A .. Cropper. A., Capistrano.D., Carpenter, S.R., Chopra, K., Dasgupta, P.,Dietz, T., Duraiappah, A.K., Hassan. R..Kasperson, R., Leemans, R., May. R.M ..McMichael, A.J .. Pingali, P., Samper. C ..Scholes, R., Watson, R.T.. Zakri. A.H .. Shidong,Z., Ash, N.J., Bennett, E., Kumar, P., Lee,M.J .. Raudsepp-Hearne, e., Simons. H., Thonell.J. and Zurek, M.B. (Eds.) 2005. Ecosyslemsand Human Well-being: Synlhesis. Island Press.Washington. District of Columbia. 155 pp.

Saini. B.S. 1980. Building in HOI Dry Cli/llales.John Wiley & Sons, Chichester.

Schreider, G. and Knerr, B. 2000. Labor migrationas a social security mechanism for smallholderhouseholds in sub-Saharan Africa: the case ofCameroon. Oxford Oevelop/llenl Sludies 28:223-236.

Schwinning, S. and Sala. O.E. 2004. Hierarchy ofresponses to resource pulses in arid and semi-aridecosystems. Oecologia 141: 211-220.

Scott, M.J .. Gupta, S .. Jauregui, E., Nwafor J.,Satterthwaite, D., Wanasinghe, Y., Wilbanks.T., Yoshino, M. and Kelkar, U. 2001. Humansettlements, energy, and industry. In C1imaleChange 200 J: J/Ilpacls, Adapralion. and

CLIMATE CHANGE AND URBANIZATION 471

Vulnerability. Contribution of Working Groupto the Third Assessment Report of theIntergovernmental Panel on Climate Change(Eds. U. McCarthy, O.F. Canziani, N.A. Leary,DJ. Dokken and K.S. White). pp. 381-416.Cambridge University Press, Cambridge.

Seely. M.K., Klintenberg, P. and Kruger, A.S.2009.The unmet challenge of connecting scientificresearch with community action. In The Fulllreof Drylands (Eds. Cathy Lee and ThomasSchaaf), pp. 687-697. Springer Netherlands &UNESCO.

Smith, S.D., Huxman, T.E .. Zitzer, S.F., Charlet,T.N., Housman. D.C., Coleman, 1.S.,Fenstermaker, L.K., Seemann, J.R. and Nowak,R.S. 2000. Elevated C02 increases productivityand invasive species success in an aridecosystem. Nalllre 408: 79-82.

Smithson. P., Addison, K. and Atkinson, K. 2002.Fundamelllal of the Physical Environmelll. 3rd

edition, Routledge Press: London and NewYork., pp. 546-564.

Stott. P.A. and Kettleborough, J.A. 2002. Originsand estimates of uncertainty in predictions oftwenty-first century temperature rise. Nalllre416: 723-726.

Tarbuck, EJ. and Lutgens, F. 2005. Earth - anIntroduction to Physical Geology. PearsonEducation Limit, New Jersey, pp. 567-589.

Thomas. D.S.G. and Leason, H.C. 2005. Dunefieldactivity response to climate variability in thesouthwest Kalahari. Geomorphology 64:117-132.

Tiffen. M. 2003. Transition in sub-Saharan Africa:agriculture, urbanization and income growth.World Development 31: 1343-1366.

Tourre. Y.. Paz. S., Cassou, C. and Kutiel, H. 2006.Atmospheric Dynamics over Northwest Africaand Linkages with Sahelian Rainfall.Geophysical Research Letters, 33, Ll4808,doi: 10.1029/2006GL026695.

UN Habitat. 2003. Water and Sanitation in the World'sCities. Earthscan, London 274 pp.

UNEP (United Nations Environment Programme)2002. Global Environmelll Outlook 3, Earthscan,London. 426 pp.

United Nations 2006. World Urbanization Prospects:the 2005 Revision. United Nations Departmentof Economic and Social Affairs, PopulationDivision, CDROM Edition - Data in digitalform (POP/DB/WUP/Rev.2005), UnitedNations, New York.

United Nations Environment Programme (UNEP)2007. Environmental Degradation TriggeringTensions and Connict in Sudan. Available:http://www.unep.org/Documents.Multi IinguallDefault.asp?DocumentlD=512&A rticlelD=5621&I=en

USGS 1997. Desertification. Available: http://pubs.usgs. govi gipidesertsl dese rti ficatio'nl

Wang, F.T. 2002. Advances in climate warmingimpacts research in China in recent ten years.Journal of Applied Meteorological Science 13:766.

Warner, T.T. 2004. Desert Meteorology. CambridgeUniversity Press, Cambridge, 595 pp.

Wenhui, Z. and Yubin, Z. 2005. On four regionalpolicy readjustments since reform and anassessment. Discussion paper. Beijing: ChinaDevelopment Institute.

Wigley, T.M.L. and Raper, S.C.B. 2001. Interpretationof high projections for global-mean warming.Science 293: 451-454.

Wittig, R., Konig, K., Schmidt, M. and Szarzynski.J. 2007. A Study of Climate Change andAnthropogenic Impacts in West Africa.Environmelllal Science and Pollution Research14(3): 182-189.

WMO (World Meteorological Organization) 2006.Drought monitoring and early warning: concepts,progress and future challenges. WMO-No. 1006;ISBN 92-63-11006-9, 24 pp.

World Research Institute 2003. Earth Trends.Washington, DC.

Yousif, H.M. 2005. Rapid urbanisation in Africa:impacts on housing and urban poverty. In ECA,2005, Assessing Sustainable Developmelll inAfrica. Assessing Sustainable Developmelll inAfrica, Africa?s Sustainable DevelopmemBulletin, Economic Commission for Africa,Addis Ababa, 55-59.