Science Opportunities - Basic Research Opportunities in Earth Science - page 38

the albedo of land vegetation, burial of organic carbon, production of
biogenic compounds such as dimethyl sulfide that affect cloud formation, and
linkages between oceanic biological productivity and iron and phosphorus
supply) are becoming important parameters in global change models. Pollen data
from cores, corroborated by isotopic and chemical evidence from reef corals,
equatorial glaciers, and groundwater, provided the first evidence of tropical
cooling during the Last Glacial Maximum, causing reconsideration of heat
transport in global circulation models (GCMs). Paleobotanical evidence from the
western United States in the late Paleocene has significantly refined the treatment
of orographic effects in GCMs during rapid warming events, and evidence of
extensive warm climate vertebrates and plants near the Cretaceous poles provides
important constraints for modeling times of extreme warmth.
Biological Controls on Earth Chemistry
The pathways and extent to which organisms fundamentally control the
distribution of elements (and isotopes) in the Earth's crust are now beginning to
be understood. Most of the iron, sulfur, phosphorus, carbon, and nitrogen in soils
and sediments pass through biological repositories, and there is growing evidence
that metabolic processes have detectable effects on other major (e.g., Ca, Si) and
minor (e.g., As, Mo, U) elements in seawater. Results of such studies provide the
mechanistic basis for modeling biogeochemical cycles and for environmental
studies of the mobility and fate of toxic compounds. New insights into the roles
of microbial metabolism, organic chelators, and sediment-irrigating and -
advecting plants and animals in processes such as mineral dissolution, mineral
precipitation, soil formation, and sedimentary diagenesis are opening the way for
more detailed understanding of Critical Zone processes both modern and ancient.
Molecular Geobiology
New data from molecular biology, developmental biology, and paleontology
have invigorated studies of the origins, evolution, and ecology of major
biological groups. Important advances include the construction of evolutionary
trees of all living things, based primarily on genetic similarities of living taxa, and
the placement of the major branching events of these trees into their correct
geological context ( Figure 2.5 ). Improvements in instrumentation and
preparative techniques have made it possible to identify and characterize the
isotopic composition of biomarker molecules in sedimentary rocks, providing
evidence for the operation of metabolic pathways important in biogeochemical