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Initial Research Priorities for U.S.
Participation in the IGBP
In this chapter, the committee identifies a number of the most
critical gaps in our understancling of global change that most ur-
gently need to be addressed in the initial U.S. contributions to the
IGBP. The several research initiatives that are recommended in this
chapter provide a framework for U.S. contributions to the IGBP in
the current planning stage of the program's development. These rec-
ommendations are not intended to include all future research needs
for the program, but are intended to emphasize those issues not being
addressed by ongoing programs.
The committee adopter! the following criteria for selecting these
initial research initiatives:
~ The issue must be global in nature, and research conducted on
the topic must be expected to lead rapidly to a greater understanding
of global environmental change.
~ The magnitude and breadth of the issue must transcend the
boundaries of existing research programs and discipline-oriented en-
deavors, making it unlikely that it-can be addressed within traditional
disciplinary studies.
~ The issue must be amenable to research, with significant
progress expected in a period of a few to 10 years or with immediate
initiation required in order to build the Tong-term monitoring and
13
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14
research base needed for sustained progress in understanding global
change.
The research initiatives are recommender! on the basis of the
committee's systematic review of the current state of knowledge
from five perspectives on the earth system: climatic and hydrologic
systems, ecological systems and dynamics, biogeochemical dynamics,
the human dimension of global change, and earth system history (see
the background papers in Part II for detailed discussions). From
these analyses particularly from analysis of the interactions among
these five components of the earth system and from a review of
related ongoing programs, the committee identified a number of
questions about key relationships that are currently insufficiently
understood but essential to improving scientific abilities to predict
global change, for example:
~ How is the climate system coupled to the dynamics of terres-
trial ecosystems, and, specifically, what are the feedbacks between
ecosystem dynamics and the hydrologic component of the climate
system?
· What factors control fluxes of radiatively active gases be-
tween the land and atmosphere and fluxes of biologically important
elements from land to aquatic systems? What are the feedbacks
between climate change and fluxes of these materials?
What are the fluxes of biogenic substances from the upper
ocean to both the atmosphere and the deep ocean? How do these
fluxes affect climate, and how does climate change affect these flux
rates?
How is the coupling of human and enviornmental systems
altered by long-term global trends in social, economic, and techno-
logical development? How is the coupling altered by environmental
change itself.
RESEARCH INITIATIVES FOR EARLY IMPLEMENTATION
.
Answering these key questions about the earth system demands
improved understanding of the influences of terrestrial and oceanic
biota on the climate system, and the interactions with the hydrologic
cycle, nutrient supply and transport, and surface climate conditions.
Answers also depend on an understanding of how anthropogenic
activities generate trace gases through changing land use, energy
production, and industrial processes.
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The committee recommends that these gaps be addressed
through major research initiatives on each of the following topics:
· Water-energy-vegetation interactions the coupling between
the climate system, especially its hydrological processes, and the
dynamics of terrestrial vegetation.
~ Fluxes of radiatively active trace gases and nutrients to and
from the terrestrial biosphere.
· Biogeochemical dynamics in the ocean that regulate formation
and influence the ocean's capacity to sequester or release radiatively
active gases, such as carbon dioxide and organic sulfur species, and
their interactions with climate.
Earth system history and modeling to reconstruct the record
of the past preserved in ice cores, sediment deposits, and other proxy
indicators of change.
Human interactions with the gloom environment to document
and analyze land use changes and changes in industrial production
and consumption over the past several hundred years, and to create
useful scenarios of future changes in the processes that drive global
change.
Issues that need to be addressed in each of these initiatives
are discussed below. These discussions, however, only outline the
broad initiatives that should be pursued and illustrate the types of
experiments, modeling efforts, and observations that wiB be required.
Detailed research plans and schedules must be formulated by groups
of experts engaged in the relevant research disciplines.
Water- Energy-Vegetation Interactions
The committee recommends an observational and research
project a water-energy-vegetation experiment to study the cou-
pling between the climate system, especially its hydrological pro-
cesses, and the dynamics of terrestrial vegetation. The initiative
has two objectives: (1) to develop validated global models of the
response of terrestrial ecosystems to climate, water and land use
change, atmospheric chemistry, and other global- or regional-scale
stress factors such as changing atmospheric composition, fires, her-
bivory, and disease; and (2) to determine how ecosystem structure
and function affect evapotranspiration, soil moisture, and surface
runoff on regional and global scales. The project would in essence
be the biological complement to the Global Energy and Water Cycle
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Experiment (GEWEX), whose planning is just now beginning under
the WCRP.
This research initiative will require field and laboratory experi-
ments, modeling efforts, and observations to address the response of
ecosystems to climate changes, as well as the response of climate to
ecosystem change. Included would be the following:
Experiments on whole ecosystems in order to quantify effects
of climate change and other stress factors.
~ Studies to scale up information on nutrient cycling and plant
physiological processes to the level of the whole ecosystem, taking
into account the dynamics of key species.
~ Recovery of records of past vegetation cover and other intli-
cators suitable for validating the long-term hydrological response of
climate models to global change.
~ Development of models of global and regional climate that
emphasize hydrological and land surface processes (using parame-
terizations derived and validated by field data and process studies)
and that can be used to study the sensitivity of climate processes to
vegetation changes.
Analysis of the human causes and effects of changes in the
hydrologic cycle, including documenting past and projecting future
human activities important for the hydrologic cycle; defining those
aspects of hydrologic change most important for human activities;
and (leveloping frameworks for application of hy(lrologic projections
to environmental assessment and management.
~ Observations at a global scale of seasonal and interannu~
variations in vegetation cover and evapotranspiration.
A regional focus to study the coupling between vegetation and
the hydrologic cycle in particularly important or sensitive geographic
regions such as the Amazon Basin, the taiga-tundra transition zone,
and the western United States is an important component of this
initiative. Such a focus includes projections of the impacts of changes
in terrestrial hyclrologic processes on ecosystem composition and
~ , - · ~
unctlomng in speclnc regions.
The initiative also requires strong input from other international
research programs, such as GEWEX and the International Satellite
Land-Surface Climatology Project (ISI:SCP), to address the ques-
tions of global distributions of rainfall over land and atmospheric
properties important for surface evapotranspiration.
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Fluxes of Radiatively Active Trace Gases and Nutrients
to and Mom the Terrestrial Biosphere
The committee proposes a research initiative focused on the
fluxes of materials such as (1) radiatively active trace gases to and
from the terrestrial biosphere, and (2) nutrients from land to aquatic
and marine ecosystems.
The objective of a research focus on radiatively active trace gas
exchange between the terrestrial biosphere and the atmosphere is
to improve understanding of those basic ecosystem processes that
determine gas fluxes. This understanding is needed to construct
functional models that can be used to predict how climate and land
use change wiD alter emissions and absorption of radiatively active
trace gases from the biosphere and, in turn, feed back to further
changes in climate. The research should emphasize methane, carbon
dioxide, and nitrous oxide, but other significant constituents, e.g.,
ammonia and organic compounds, are also of concern.
The initiative will require the following:
· Experiments involving plants, soils, and peats to improve un-
derstanding of processes affecting gas exchange between them and
the atmosphere, such as changes in carbon storage; the influence of
nutrient availability; the influence of population dynamics through
nitrogen fixation, and microbial processes; hydrological influences
on partitioning between production of carbon dioxide and methane
and between nitrogen and nitrous oxide; and the influence of the
chemistry of precipitation on such processes. Experiments on in-
tact ecosystems that include the biota and soils will also be needed
to measure the effect of environmental changes on the complex, in-
teracting processes of vegetation change, nutrient cycling, and gas
fluxes. Larger scale ecosystem experiments can involve, for example,
manipulations of entire watersheds or can use natural or inadvertent
anthropogenically induced perturbations for experiments.
· Investigations at local or regional scales, particularly in ecosys-
tems such as the Arctic and the tropics that play significant roles
in global change. A local and regional focus, including compara-
tive studies along environmental gradients, is needed in order to
extrapolate predictions of gas emissions to the global scale after a
mechanistic understanding of gas emissions is achieved.
· Models that combine descriptions of the functioning of whole
ecosystems (process-functional approach) with descriptions of
changes in populations and communities within ecosystems (popula-
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tion-community approach), in order to predict the changing patterns
of fluxes from ecosystems subjected to rapid change. Because this
new generation of models wiB be mechanistic, they could be used to
extrapolate beyond existing or past conditions, and to predict gas
emissions from new combinations of vegetation, soils, climate, land
use, and atmospheric processes.
· Increased attention to documentation of past ecosystems from
the record of the past, in order to understand better the range of
ecosystem form and function that could develop in the future in
response to global change.
· Documentation on a global scale of the history of land uses
believed to be sources of methane and other trace gases, and as-
sessments of future changes in human activities that can result in
changes in emissions. Similarly, prehistoric and historic activities
that have affected carbon storage in vegetation and soils should be
documented on a global scale.
The component of this research initiative focused on fluxes of nu-
trients from terrestrial to aquatic systems will, in addition to study-
ing nutrient transfers in natural ecosystems, emphasize the effects of
land use change on the amount and pathways of nutrient losses from
terrestrial ecosystems. The objective is to broaden the initiative on
trace gas emissions to include analysis of how global changes now
under way will affect the transfer of nutrients to riverine, estuarine,
and ultimately, ocean systems. As discussed in the following section,
changes in ocean productivity have important long-term implications
for climate. Thus nutrient transfers from the terrestrial to marine
systems could have important feedback effects.
Transfers of materials across ecosystem boundaries will be
strongly affected by various aspects of global change. I,arge-scale
experiments, involving manipulations of entire watersheds or intact
ecosystems, are needed to assess the effects on nutrient Tosses of
floods, increased fire frequency, loss of species, and other events
related to global change. Rising sea level will also affect nutrient
cycling and transfer to the ocean. Superimposed on these effects,
and in some systems overwhelming them, are massive changes in
land use, especially in the tropics, where the human population and
activity are growing rapidly. Deforestation and increased intensity of
agriculture in dry and humid tropical regions are affecting nutrient
availability in soils and transfers to other systems via dust and runoff.
Understanding the processes underlying nutrient Tosses from ter-
restrial systems will require monitored watersheds. Once baseline
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data are established, experiments with different kinds of land use
can be carried out, with paired watersheds left unchanged as con-
trols. These experiments will separate human effects from other
aspects of global change. Long-term observations are necessary, as
some effects are cumulative and others have long response times.
Long-term studies will also increase the opportunity to observe and
hence understand unusual climatic events that stress the system.
The important requirements are thus as follows:
~ Experimental manipulations of drainage basins to increase
understanding of the mechanisms controlling nutrient transfer via
water or air from the land to streams, lakes, rivers, and eventually,
the ocean.
~ Examinations of systems along a gradient, e.g., from savanna
to dry forest to rain forest, in order to quantify fluxes as a function
of ecosystem type.
Research to follow the fate of nutrients after they are lost from
terrestrial ecosystems into rivers, lakes, groundwater, the ocean, and
the atmosphere. Studies of estuarine processing of nutrients loaded
into rivers should be emphasized.
Analysis of the patterns and causes of anthropogenic land use
change, including documenting past and projecting future human
activities important for terrestrial nutrient fluxes, and defining those
aspects of nutrient flux most important for human activities.
~ _ _1~ 1 _ _ 1 · 1 1 · ~ · , ~ ~
.
rartlcular emphasis on phosphorus In nutrient balance stud-
ies. While phosphorus is less mobile and dynamic than carbon,
nitrogen, and sulfur, it exerts a strong control on productivity both
on land and in aquatic systems.
Some approaches appear promising in the context of this research
focus. For example, stable isotope signatures of carbon, nitrogen, and
sulfur as tracers of element movement and as integrated reflections of
the processes controlling element transformation and loss will provide
important information. While this approach is relatively well worked
out for carbon, considerable development of research techniques is
necessary before it can be applied to nitrogen and sulfur. Better
measurements of both historic and current rates and types of land
conversion also need to be developed and applied.
Collaboration with the research component on fluxes of radia-
tively active gas, discussed above, is needed to understand, model,
and predict biosphere-atmosphere interaction following land clearing.
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Additionally, interaction with ongoing programs such as the Inter-
national Union of Biological Science's Tropical Biology and Fertility
Program and the International Atomic Energy Association-Centro
Energia Nuclear na Agricultura (TAEA-CENA) Amazonia ~ Project
will be needed for the research focus discussed here.
The overall initiative should be linked with activities of experts
concerned with land use change as a primary driving force in species
extinctions worldwide (see "Human Interactions" initiative below).
Both the information on rates of land use change and the measure-
ments of the fate of nutrients once they are lost from cleared land
are fundamental to these efforts, and knowledge of the functional
significance of particular species in local areas is fundamental to this
initiative.
Biogeochemical Dynamics in the Ocean
The committee recommends a research initiative to understand
and predict the effects of climate change on ocean biogeochemical
cycles and their corresponding feedback to climate. 'the objective
of this effort is to develop the capability to predict the effect of
projected global climate change on the ocean's physical/chemical
and biogeochemical processes, especially as they feed back to climate
via the release or absorption of radiatively important gases such as
carbon dioxide and organic sulfur species.
Changes in climate over the ocean will alter the physical condi-
tions of the upper ocean. Incident irradiation, evaporation/precipita-
tion, and wind shears on the ocean surface help to define the mixing
state, and hence the nutrient supply and residence time for plankton.
Nutrient supply and re-suspension properties are important factors
in determining the nature of the planktonic food web. Greater rates
of nutrient supply, and higher mixing rates, for example, promote
the growth of large diatoms. These two different types of plankton
sustain markedly different food webs and have significantly differ-
ent consequences for the residence time of photosynthetically fixed
carbon in the ocean. In addition, different plankton groups have
different physiologies related to sulfur metabolism and play consid-
erably different roles in the evolution of organic sulfur species, which
have climatic implications when liberated to the atmosphere.
This effort will require a gIobaI-scaTe assessment of the processes
governing the rates of primary production and determining the fate
of biogenic materials in the sea. A major international program, the
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Joint Global Ocean Flux Study (JGOFS) is now being defined in this
area. It will consist of global observations, regional process studies,
coastal ocean studies, and modeling. Some of the recommendations
below will probably be included in JGOFS, some should be initiated
as soon as possible, while other activities, especially those related to
the biogeochemical implications of the anticipated climate change,
may require results of JGOFS and other ocean programs such as the
World Ocean Circulation Experiment before they can be initiated.
A U.S. contribution in this area should include the following:
Helping to establish the global remote sensing capability and
appropriate sea surface verification necessary to assess temporal and
spatial patterns in plankton distribution.
~ Studying the processes responsible for the initiation of plank-
ton blooms (including dependence on temperature, mixing state, and
nutrient supply) and their roles in (1) the flux of organic material
and calcium carbonate to the deep sea and (2) the production of
organic sulfur compounds, which, when liberated to the atmosphere,
have implications for climate.
~ Developing modeling and scaling techniques to generalize the
results of intensive local studies of plankton blooms to characteristic
regional and basin scales.
~ Placing emphasis on those high-latitude ocean regions where
vertical fluxes of carbon to the deep sea and vertical fluxes of nutri-
ents to the surface waters give these regions disproportionately large
global significance.
· Investigating the biogeochemical processes responsible for
forming, transporting, and preserving in ocean sediments the hard
parts of plankton used in studies of past climates.
~ Initiating large-scale models of upper ocean physical and bio-
geochemical processes that can be used to assess the effects of climate
change on biogeochemical processes that have potential to feed back
to climate via the regulation of radiatively active trace gas release
from the ocean.
Human Interactions with Global Change
This research initiative would focus on the relatively short-term
record of the period of intensive human activities that have affected
the global environment. Anthropogenic changes in the earth system
need to be systematically documented over the past several hundred
years and analyzed as a basis for developing useful reference scenarios
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of future change. In particular, two aspects of human activity are es-
peciaDy relevant to global change: land use changes, which influence
both physical (e.g., albedo, evapotranspiration, and trace gas flux)
and biological (e.g., vegetative cover and biodiversity) variables; and
the industrial metabolism that transforms resources into emissions
that must be absorbed and processed by the environment.
Investigation of global land use patterns would involve the fol-
lowing:
~ Construction of a core conceptual mode] or theory of the
causal relations underlying: changes in culture be.. Copulation. de-
_ _ ~ ~ ~ ~ ~
velopment values) on one hand and changes in environment on the
other hand, to human choices that affect long-term, large-scale pat-
terns in the use of land.
· Documentation of how key variables of land use, population,
agricultural prices, and so on, identified in the conceptual mode! have
changed throughout the world over the last several hundred years.
In-depth regional case studies of the general relationships
suggested in the conceptual and historical work.
· Construction of future scenarios of global land use change,
and exploration of how alternative human choices regarding global
change could alter those scenarios.
Parallel to the study of global land use change, a similar approach to
the study of industrial metabolism would involve the following:
Construction of a conceptual model linking demographic, eco-
nomic, and institutional factors with the evolution of material and
energy uses, and human consumption processes relevant to global
change.
Documentation of how particular material and energy re-
sources have been metabolized through human production and con-
gumption processes over periods of decades to centuries.
In-depth regional case studies of the general relationships
developed in the conceptual and historical work.
Construction of future scenarios of industrial metabolism and
associated materials and energy exchanges with the environment.
Earth System History and Modeling
The initiative on earth system history and modeling is con-
cerned with documenting and understanding overall patterns of
global change. The initiative would focus on reconstructing the past
... .. .. . . .
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over tens of thousands of years to provide a data base for validating
global change models. The history of atmospheric composition arid
climate, and of the spatial distribution of climate, vegetation, and
ocean circulation would be developed. Special attention is needed
on periods of rapid change to provide insight into poorly understood
system processes.
A research focus on the long-term record requires the following:
.
Data from polar and temperate latitude ice cores, ocean sed-
iments and corals with 10- to 100-year temporal resolution, and
various kinds of physical and biological terrestrial records.
· Theoretical studies and modeling to establish quantitative
relationships between measured parameters and physical processes,
in order to better interpret the record of the past.
· Sensitivity studies with global models to define the spatial
and temporal resolution needed in the study of the record of the past
and to suggest which types of data should be collected.
~ Development and improvement of global change models based
on observations from the record of the past. Models can use infor-
mation from the past record such as climate and vegetation and
indirect measures of the carbon cycle. Past abundance of carbon
dioxide, methane, carbon-13 and other stable isotopes, and other
chemical species accessible from the record can be used for model
validation. Data on the history of human interactions with the earth
system, as developed in the previous initiative, will also be useful.
Close collaboration between observational and modeling activities is
essential.
DEVELOPMENT OF RESEARCH INITIATIVES
Two streams of activity are required to develop the research
initiatives for the U.S. contribution to the IGBP into detailed plans
for research programs: (1) involvement of scientists with particular
expertise to develop the research plans, and (2) support of those
related activities essential to the success of the IGBP.
Steering groups should be established on each of the five research
initiatives proposed above as research foci for the initial contribution
to the IGBP. These groups should be closely coordinated with other
relevant activities in the National Research Council. These steer-
ing groups, operating under the Committee on Global Change over
approximately the next two years, would engage scientists with the
relevant expertise to further define programs of coordinated research
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in the respective area. The Committee on Global Change would en-
sure that the research plans developed by each group are coordinated
into an overall plan for the U.S. contribution to the IGBP.
Support for existing programs related to the goals for the IGBP
is also an integral part of the U.S. effort. Three categories of support
can be identified:
1. As noted above, U.S. contributions to the IGBP are drawn
from the broad suite of U.S. observational and research programs
that have been described as the U.S. effort on global change. The
U.S. program is based on the concept developed in the report of
the NASA-sponsored Earth System Sciences Committee that study
of the earth as an integrated system is an important and timely
paradigm for the earth sciences. Strong support for such a broad
national effort in the study of the earth is an essential foundation for
the focused programs addressed in this report.
2. A number of existing, ongoing programs have objectives and
weD-developed plans that clearly fall entirely or partly within the
scope of the IGBP or the broader U.S. global change efforts. Among
these are UNESCO's Man and the Biosphere Program, the several
projects of the Scientific Committee on Problems of the Environment
related to global change, and the United Nations Environment Pro-
gram's Global Environmental Monitoring System (GEMS). Particu-
larly relevant and essential are the components of the World Climate
Program. One of these, the World Climate Research Program, or-
ganized under the World Meteorological Organization (WMO) and
ICSU, focuses on dynamic and hydrological processes in the climate
system and has in planning or in progress a number of well-conceived
projects (e.g., Global Energy and Water Cycle Experiment, World
Ocean Circulation Experiment, Tropical Ocean/GIobal Atmosphere
Program, International Satellite Cloud Climatology Project, and In-
ternational Satellite Land-Surface Climatology Project) that promise
to contribute greatly to the goals of the IGBP. The contributions of
the Data, Applications, and Impacts components of the World CTi-
mate Program should also be emphasized. The IGBP and these
existing activities are highly complementary en cl mutually support-
~ve.
The challenge is to harmonize and coordinate the practical work
of the various planning bodies so that each activity can be effec-
tively focused on appropriate objectives. Such an approach was
successfully employed in the Global Atmospheric Research Program
(GARP), where the WMO/ICSU Joint Organizing Committee, the
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ICSU Committee on Space Research, the International Association
of Meteorology and Atmospheric Physics' (lAMAP) Radiation Com-
mission, and other bodies pursued closely coordinated programs.
Interaction within this family of closely related activities in the earth
sciences should be strengthened, coordinated, and enhanced.
3. Support for discipline-oriented research related to the goals
of the IGBP is needed to bolster the scientific foundations of the
program. For research centered on the atmospheric and oceanic
components, a long and mature history of previous studies and an
array of coordinated research programs provide good foundations
for contributions to the understanding of global change. In other
areas, such as the biological and human components of global change,
the existing research program is less wed developed. The relevant
research communities should be encouraged to develop their own
internally justified research priorities relevant to global change. An
aggressive program to support research in these as well as other
related disciplines is needed.
For instance, a number of areas of needed research are highlighted
in the background paper on ecological systems and dynamics (see
especially the section on principal issues and research challenges).
These include (1) research on physiological responses of plants and
animals to the environment, especially to multiple stresses; patterns
of genetic variability, including the development of theory regarding
evolutionary responses to rapid environmental change; the direct ef-
fects of elevated carbon dioxide concentrations on intact ecosystems;
and characteristics that allow some species to adjust geographical
ranges rapidly in the face of change while others become extinct;
(2) monitoring of ongoing changes in distributions that may record
the incipient effects of global change and of ongoing changes in Tend
use; and (3) development of more complete paleorecords, particularly
from littIe-explored parts of the earth.
The existing research program on the human components of
global change is also inadequately developed, as discussed in the
background paper on the human dimension. Efforts to bring to-
gether natural, social, behavioral, and engineering scientists to ex-
amine in-depth the research required on the human dimension of
global change should be supported. Several research areas identified
in the background paper integrated methods to assess the risk and
implications of Tong-term environmental change for resource avail-
ability at the regional scale; ways that knowledge, perceptions, and
values related to global change can be more effectively brought to
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bear on human choices that affect global change; and evaluation
and design of institutional mechanisms for better management of
global change require further development in close collaboration
with those relevant scientific communities in the social, behavioral,
and engineering sciences that were not adequately represented in
current planning activities.
Representative terms from entire chapter:
research initiatives
