Geodiversity & Geoconservation

Historical Perspectives on and Geodiversity

Vincent L. Santucci

Introduction THE CONCEPT OF GEODIVERSITY HAS COME TO RECENT ATTENTION largely due to the work and publications of geologist Murray Gray. In his book, Geodiversity: Valuing and Conserving Abiotic Nature, Gray presents a comprehensive thesis assessing the role and sig- nificance of abiotic resources upon biotic resources (Gray 2004). A basic premise of the geodiversity Modern relationships concept recognizes that there is an intrinsic In recent decades the relationships relationship between biological diversity between biodiversity and geodiversity have and geological diversity. In principle, the become more recognized by modern ecolo- geologic bedrock is viewed as the founda- gists and natural resource specialists. An tion of the ecosystem. Geologic resources increasing number of research publications and processes sustain much greater rela- and conferences focus on the integration of tionships with biotic resources and biosys- modern “bio-geo systems.” The relation- tems than is commonly recognized. These ships can be examined at the microscopic relationships are integrated at the ecosys- through the global levels of resolution. tem, community,species, organism, cellular, Below are a number of examples of how and genetic levels. geologic resources and geodiversity influ- The relationship between biodiversity ence biotic resources. and geodiversity can be evaluated in mod- Climate. Climate can be influenced ern environments or past environments locally by geologic features and processes. (paleoenvironments). Gray’s book presents Mountain ranges can impact wind speeds a multitude of examples from around the and directions, as well as form rain shad- world demonstrating the inherent relation- ows. Volcanic eruptions generating large ships and patterns between modern biotic volumes of ash may be transported great and abiotic resources. Similarly, the fossil distances and influence regional climatic record preserves excellent examples of rela- conditions. tionships between ancient organisms and Hydrology. Hydrology is largely con- paleoenvironments. Research focused on trolled by geology and geomorphology.The paleoecological changes or trends over time distribution of drainages, watersheds, may enable greater understanding of the aquifers, seeps, and springs are linked to influences that geologic resources may have lithologic and stratigraphic contacts and exerted over biotic resources in the past. geomorphic features. Lakes form within

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Geodiversity & Geoconservation calderas, karst topography, periglacial changes in sea level can result in the con- zones, and where landslides or basalt flows nection or separation of land masses, in turn dam river valleys. Additionally, chem- resulting in either the direct competition or istry, salinity, and other variables influenc- geographic isolation of biota. ing biodiversity are directly associated with geologic resources. Historical geologic and biological views . Soils are the link between the Geologists are trained to assess the past abiotic and biotic worlds. composition through evidence and information pre- and chemistry are directly related to the served within rock units. Discernable char- underlying bedrock. Consequently, the dis- acteristics such as composition, tribution of many plant taxa is dependent textures, morphology, and bed- upon the mineralogical and chemical com- ding often yield detailed information position of the soil. Resource management regarding ancient depositional environ- staff at Capitol Reef National Park have ments. been able to use geologic maps and soils Not all paleontologists spend their maps to locate rare and endangered species careers hunting for dinosaurs. Scores of of cacti which grow directly and sometimes specialists have dedicated their careers in exclusively within soils developed in the order to establish scientific credibility in the Jurassic Morrison Formation. fields of paleoecology, paleogeography, Habitat. The diversity of geologic fea- paleoclimatology, and related disciplines. tures and processes provides an almost infi- The opportunity to assess both geologic nite array of habitat types to sustain life. and paleontologic data over long spans of Changes in elevation between intermontane geologic time is powerful. Historic biologi- basins and mountain ranges typically tran- cal and historic geologic data discernable in scend multiple life zones; geothermal the stratigraphic record may be of great springs sustain nutrients and temperatures benefit to the modern ecologist. required by certain forms of cyanobacteria Geologic time scale. The division of (Figure 1); caves fissures, talus slopes, and geologic time is not arbitrary, but has been gypsum sands support species adapted to based upon significant geologic and paleo- survive in these geologic environments. biologic events. Major boundaries estab- Biogeographic distribution. The geo- lished in the geologic time scale often repre- graphic distribution of fauna and flora is sent mass extinction and speciation events. well studied. Range maps for modern Research from around the world, which has species are typically illustrated in natural been incorporated into the geologic time history field guides. Geographic ranges and scale, consistently support the concept of migration routes are often influenced by changes in past biodiversity are often tied to surficial geomorphology. Mountain ranges, changes in geodiversity. canyons, deserts, water bodies, and other Extinction. Extinction has been com- geologic features may either represent corri- prehensively examined by both modern dors or barriers to migration. Paleonto- biologists and paleobiologists (Raup and logical records show that historic ranges for Sepkoski 1982, 1986). Despite the hopes taxa may change over time, often related to and efforts to establish a simple explanation geologic factors. Continental drift and for extinction, such as a meteor impact, our 30 The George Wright Forum

Geodiversity & Geoconservation understanding of extinction re- mains limited. Certainly mass ex- tinctions, which transcend taxo- nomic boundaries, are somehow linked to large-scale change in abi- otic resources. Speciation. Just as biodiver- sity is dependent upon geodiversi- ty, biodiversity is a function of genetic diversity. Questions per- taining to systematics and evolu- tion are typically better addressed by way of paleontological re- sources than by modern species. Figure 1. Cyanobacteria in a thermal pool at Yellowstone National Park. Photo courtesy of the author The fossil record contains an abundance of evidence to derive phylogenetic relationships and evolutionary The rich Ediacaran fauna overturned trends (Raup 1981). the long-held misconception that biological Origin of life. The adaptability of life diversity during the Precambrian was low. is well demonstrated in the geothermal In fact, since the discovery at Ediacara, pools of Yellowstone National Park. fieldwork in Precambrian rocks has yielded Cyanobacteria thrive within the high-tem- numerous other localities around the world perature, mineral-rich hot springs, demon- preserving these mysterious soft-bodied strating an interesting example of a close organisms—experiments in the early evolu- relationship between biotic and abiotic tion of life. resources. The existence of high-tempera- Cambrian explosion. The beginning ture cyanobacteria in Yellowstone hot of the Paleozoic, referred to as the springs is considered important in research Cambrian, is defined by the almost sudden, associated with the origin of life on earth worldwide explosion of life forms, in terms and the existence of life on other planets of both diversity and abundance. This per- (Reysenbach, in press). ceived biotic explosion is more directly tied Early biodiversity / Ediacara fauna. to the chemical evolution of the atmosphere One of the most interesting and important paleontological discoveries occurred in a series of very old rocks in the Ediacara Hills of Australia (McMenamin 1998). Fine- grained Precambrian sedimentary rocks, deposited in a low-energy environment, preserve beautiful and delicate remains of soft-bodied organisms (Figure 2). These rare and unusual life forms provide an exceptional view of early biodiversity on earth. Figure 2. An Ediacaran fossil. Photo courtesy of the author Volume 22 • Number 3 (2005) 31

Geodiversity & Geoconservation with sufficient concentrations of oxygen quences, representing eustatic sea-level available for organisms to precipitate calci- changes, punctuate the Paleozoic era. um carbonate exoskeletons. Over the past 4 During the Cretaceous period, a shallow billion years, life has continued to evolve, inland sea extended from the Gulf of diversify, and become integrated into com- Mexico to the Arctic Ocean. This Creta- munities and ecosystems. ceous sea existed for millions of years, geo- Plate tectonics / continental drift. graphically isolating populations of terres- Modern geologic theory is based upon an trial plants and animals. understanding that the Earth’s crust con- Continental glaciation. Four cycles of sists of plates. These plates are dynamic and glacial advance and retreat are documented mobile. Geologists believe that the conti- during the Pleistocene. Continental ice nental landmasses of today were once part sheets expanded and withdrew in northern of a single landmass referred to as Pangaea. latitudes. During periods of glacial advance, The distribution of identical fossil genera a worldwide drop in sea level was experi- from Permian rock units, exposed across enced. The drop in sea level, combined four widely separated continents, provides with the expanded ice sheet, resulted in a strong evidence for the original proximity direct connection between Alaska and of these organisms and landmasses. Russia, referred to as the Bering Land Mountain building / orogeny. The Bridge. geographic range and migration routes of Megafaunal migration. Changes in species can be defined by geologic and geo- sea level, expansion of continental ice morphic features. The uplift of mountain sheets, and the development of land bridges chains, development of canyons, and enabled terrestrial species to migrate into expansion of lakes are examples of geologic adjacent land masses. During the Pleisto- processes which may influence the distribu- cene, large mammals and humans were able tion and movement of biotic resources. to migrate across the Bering Land Bridge. Visitors to Grand Canyon National In turn, these mammals came into direct Park may learn about the story of the tassel- competition with existing species. eared squirrels. The Abert’s squirrel and Pleistocene cave deposits. Pleistocene Kaibab squirrel are believed to be descen- / Holocene climate changes can be docu- dents of a common ancestor. With the development of the Grand Canyon, two popula- tions of the squirrel were geo- graphically isolated. Even- tually the isolated populations evolved into distinct taxa (Figure 3). Sea-level changes. The geologic record preserves abundant evidence of changes in worldwide sea level. Trans- Figure 3. An example of geomorphically induced reproductive isolation: the distinc- gressive and regressive se- tive Abert’s (A) and Kaibab (b) squirrel. Photo courtesy of the author 32 The George Wright Forum

Geodiversity & Geoconservation mented through analysis of packrat mid- Charles Darwin’s contributions to natural dens and fossiliferous cave deposits (San- science. Darwin proposed new ideas put tucci et al. 2001). In classic studies under- forth in On the Origin of Species and other taken by the paleontologist John Guilday, publications based upon observations and fossil-rich sequences of Pleistocene strata data accumulated on a global scale. Over were excavated from sinkholes and caves of the past half-century, natural science has the Appalachian states (Guilday and shifted its focus in education, research, and Hamilton 1978). The stratified cave sedi- funding away from the Darwin-style big- ments yielded fossil mammal remains alter- picture approach, to an emphasis on the nating between southern warm-weather cellular, genetic, and molecular levels of species and northern cold-weather species. biology. Through independent lines of evidence, it Unquestionably, we have benefited was determined that this biostratigraphic from the scientific understandings gained pattern was due to the displacement south through this microscopic and submicro- of the northern boreal species during glacial scopic trend in natural science. However, advance, and the return of the southern the cost has been a diminished ability for temperate species during glacial retreat. many scholars and students to take on the Great Smoky Mountains refugia. multidisciplinary, big-picture questions. In Great Smoky Mountains National Park is turn, we have migrated toward anthro- renowned for its rich biodiversity. This fact pocentric and biocentric strategies for natu- has been confirmed through comprehen- ral science. sive biological resource inventories in Odds are that one would more likely recent years. Part of the historic biological recognize the influence of geodiversity on story at the park is tied to the expansion of biodiversity if one lives in the shadow of a the continental ice sheets during the volcano, along an active fault line, or in the Pleistocene. During glacial advance, the path of an advancing glacier. more northern boreal and temperate spe- As we continue to integrate biotic and cies were pushed south and were eventually abiotic components of the natural world established themselves within Pleistocene into our conscience and routinely recognize refugia in the southern Appalachians. that geology is the foundation of the ecosys- tem, then we may come to fully understand The Darwinian approach that “Earth and its inhabitants have evolved In consideration of this geodiverse per- together.” spective, perhaps it is worth reflecting on

References Gray,M. 2004. Geodiversity: Valuing and Conserving Abiotic Nature. Chichester, U.K.: John Wiley & Sons. Guilday, J., and H. Hamilton, 1978. Ecological significance of displaced boreal mammals in West Virginia Caves. Journal of Mammalogy 59:176–181. McMenamin, M. 1998. The Garden of Ediacara: Discovering the First Complex Life. New

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York: Columbia University Press. Raup, D. 1981. Evolution and the fossil record. Science 213, 289. Raup, D., and J. Sepkoski. 1982. Mass extinctions in the marine fossil record. Science 215, 1501–1502. ———. 1986. Periodic extinction of families and genera. Science 231, 833–835. Reysenbach, A.-L. In press. Biodiversity, Ecology, and Evolution of Thermophiles in Yellowstone National Park: Overview and Issues. New York: Plenum Press. Santucci, V.L.,J. Kenworthy,and R. Kerbo. 2001. An inventory of paleontological resources associated with National Park Service caves. National Park Service NPS / NRGRD / GRDTR-01/02. Denver: National Park Service Geological Resources Division. On-line at www2.nature.nps.gov/geology/paleontology/pub/cavepaleo.pdf.

Vincent L. Santucci, National Park Service, George Washington Memorial Parkway,Turkey Run Park, McLean, VA 22101; [email protected]

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