Sanderson Et Al., the Human Footprint and the Last of the Wild
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Articles The Human Footprint and the Last of the Wild ERICW. SANDERSON,MALANDING JAITEH, MARC A. LEVY,KENT H. REDFORD, ANTOINETTEV. WANNEBO,AND GILLIANWOOLMER n Genesis,God blesses humanbeings and bids us to take dominion over the fish in the sea,the birdsin the air, THE HUMANFOOTPRINT IS A GLOBAL and other We are entreatedto be fruitful every living thing. MAPOF HUMANINFLUENCE ON THE and multiply,to fill the earth,and subdueit (Gen. 1:28).The bad news, and the good news, is that we have almost suc- LANDSURFACE, WHICH SUGGESTSTHAT ceeded. Thereis little debatein scientificcircles about the impor- HUMANBEINGS ARE STEWARDS OF tance of human influenceon ecosystems.According to sci- WE LIKEIT OR NOT entists'reports, we appropriateover 40%of the net primary NATURE,WHETHER productivity(the greenmaterial) produced on Eartheach year (Vitouseket al. 1986,Rojstaczer et al.2001). We consume 35% thislack of appreciationmay be dueto scientists'propensity of the productivityof the oceanicshelf (Pauly and Christensen to expressthemselves in termslike "appropriation of net pri- 1995), and we use 60% of freshwaterrun-off (Postel et al. maryproductivity" or "exponentialpopulation growth," ab- 1996). The unprecedentedescalation in both human popu- stractionsthat require some training to understand.It may lation and consumption in the 20th centuryhas resultedin be dueto historicalassumptions about and habits inherited environmentalcrises never before encountered in the history fromtimes when human beings, as a group,had dramatically of humankindand the world (McNeill2000). E. O. Wilson less influenceon the biosphere.Now the individualdeci- (2002) claims it would now take four Earthsto meet the consumptiondemands of the currenthuman population,if Eric Sanderson(e-mail: [email protected])is associatedirector, and every human consumed at the level of the averageUS in- W. Gillian Woolmeris programmanager and GIS analyst, in the Landscape habitant.The influenceof human on the planethas be- beings Ecologyand GeographicAnalysis Program at the WildlifeConservation So- to find adultsin coun- come so pervasivethat it is hard any cietyInstitute, 2300 SouthernBlvd., Bronx, NY 10460.Kent H. Redfordis di- trywho havenot seen the environmentaround them reduced rectorof the institute.MalandingJaiteh is a researchassociate and GISspe- in naturalvalues during their lifetimes-woodlots converted cialist,MarcA. Levy is associatedirector for scienceapplications, andAntoinette to lands convertedto suburbande- V Wannebois seniorstaff associate at the Centerfor InternationalEarth Sci- agriculture,agricultural ence Network Columbia 61 Route Pal- suburban convertedto urbanareas. Information (CIESIN), University, 9W, velopment, development isades,NY 10964.Sanderson's research interests include applications of land- local is the The cumulative effect of these many changes scape ecology to conservationproblems and geographicaland historical globalphenomenon of humaninfluence on nature,a new ge- contextsfor modernconservation action; he has recentlypublished scientific con- ological epoch some call the "anthropocene"(Steffen and articleson conservationplanning for landscapespecies and rangewide servation the Woolmer'sresearch interests include the 2001). Human influenceis arguablythe most impor- prioritiesfor jaguar. ap- Tyson and othertechnologies forfield and tant factor life of all kinds in world plicationofgeographic information systems affecting today's (Lande broad-basedconservation activities. Redford has written extensively about the 1998,Terborgh 1999, Pimm 2001, UNEP 2001). theoryand practice of conservation.Levy, a politicalscientist with a background Yetdespite the broadconsensus among biologists about the in internationalrelations and public policy, conducts research on international and importanceof humaninfluence on nature,this phenomenon environmentalgovernance, sustainability indicators, environment-security interactions.Jaiteh's research interests include of remotesensing and its arenot fullyappreciated by the largerhu- applications implications and technologiesin human-environment man which does not them in its eco- geographicinformation systems community, recognize interactions,particularly the dynamics of land useand coverchange in Africa. nomic systems(Hall et al. 2001) or in most of its politicalde- Wannebo'sresearch interests include detecting land useand landcover changes cisions(Soulk and Terborgh 1999, Chapin et al.2000). In part, usingremote sensing. @ 2002 AmericanInstitute of BiologicalSciences. October 2002 / Vol. 52 No. 10 * BioScience 891 Articles sions of 6 billion people add up to a globalphenomenon in turbanceindex (Hannahet al. 1994, 1995),which used dig- a way unique to our time. What we need is a way to under- itized maps from Rand-McNallyatlases and other sourcesto stand this influencethat is global in extent and yet easy to classifyareas as "human-dominated"'"partially disturbed," or grasp-what we need is a map. "undisturbed";according to thatindex, nearly three-quarters Until recently,designing such a map was not possible,be- of the habitablesurface of the planet is disturbedat least in causedetailed data on humanactivities at the globalscale were part by human use. The GlobalMethodology for Mapping unavailable.The fortunateconfluence of severalfactors dur- HumanImpacts on the Biosphere(GLOBIO; UNEP 2001) es- ing the 1990schanged this situation.Rapid advances in earth timates the amount of disturbanceon flora and fauna ac- observation,using satellite technology pioneered by NASAand cording to their distance from human infrastructure(e.g., other spaceagencies, meant that,for the firsttime, verifiable roads,pipelines, settlements). Originally focused on scenar- globalmaps of land use and land coverwere available (Love- ios of historic,current, and futureimpact in the Arcticregion, land et al. 2000). The thawingof the cold war and callsfor ef- these analyseshave recently been expanded to the global ficiencyin governmentmeant that other sources of globalge- scale (see www.globio.infofor updates). The human foot- ographic data, for example, on roads and railways,were printhas importantparallels to allthese efforts, which, though releasedto the publicby the US NationalImagery and Map- approachingthe questionusing a varietyof datasources and ping Agency (NIMA 1997). Improvedreporting of popula- methodologies,arrive at largelythe same answer. tion statisticsat subnationallevels enabled geographers to cre- To map the human footprint,we used four types of data ateglobal digital maps of humanpopulation density (CIESIN as proxies for human influence: population density, land et al. 2000). Finally,advances in geographicinformation sys- transformation, accessibility,and electrical power infra- tems (GIS)have provided the integrationtechnology neces- structure.Nine datasetsthat representthese four datatypes sary to combine these data in an efficientand reproducible (table 1) were selectedfor their coverage,consistency, avail- manner.Although the datasetsnow availableare imperfect in- ability,and relevance,but theyprovide only an incompletede- struments,they areof sufficientdetail and completenessthat scriptionof human influenceon nature.For example,most scientists can map the influence of humans on the entire of these datasetsdo not include Antarcticaor many small land'ssurface. oceanicislands, and thus we had to excludethese areasfrom Wecall our map of humaninfluence "the human footprint," our analysis.In addition,we confinedour analysisto the ter- consciousof its similarityto the ecologicalfootprint, a set of restrialrealm, because a differentset of inputs would be re- techniquesfor estimatingthe amount of land or sea neces- quiredto map human influencein the oceans.Effects of pol- saryto supportthe consumptionhabits of one individual,pop- lution, global warming, increased exposure to ultraviolet ulation,product, activity, or service (Wackernageland Rees radiation,and other globalphenomena, although they have 1996).The humanfootprint represents in some sensethe sum importantconsequences for terrestrial ecosystems, are not in- total of ecological footprints of the human population. It cluded. For this analysiswe focused on the directmeasures expressesthat sum not as a single number,however, but as a of human infrastructureand populationthat have the most continuum of human influence stretched across the land immediateimpact on wildlife and wild lands and for which surface,revealing through its variationthe majorpattern of geographicdata were readilyavailable. To combine the nine human influenceon nature. datasets,we needed to (1) presentthem in one map projec- tion, using a consistentset of coastalboundaries and regions; Mapping the human footprint (2) express them as overlaying grids at a resolution of 1 Our techniquefor mappingthe human footprintgrows out squarekilometer (km2); and (3) code each datasetinto stan- of a recenttradition of wildernessmapping (McCloskey and dardizedscores that reflectedtheir estimated contribution to Spalding 1989, Lesslieand Malsen 1995, Aplet et al. 2000, human influenceon a scale of 0 to 10 (0 for low human in- Yaroshenkoet al.2001), which focuseson defininghuman in- fluence, 10 for high). fluencethrough geographic proxies, such as human popula- These codes were based on published scientific studies tion density,settlements, roads, and other accesspoints, and and consultationwith a rangeof biologists,social scientists, includesfactors such as the size and remotenessof an area. and conservationists,as summarizedbelow.