The Biosphere: A Decadal Vision

6 Pages·2003·0.65 MB·English

by  Peterson, David L.

The Biosphere: A Decadal Vision
David L. Peterson, NASA Ames Research Center, Moffett Field CA 94035
Paul J. Curran, Southampton University, Southampton, UK
Marty Mlynzcak, Langley Research Center, Hampton VA 23681
Richard Miller, Stennis Space Center, MS 39529
I. INTRODUCTION and interactive modeling can play in developing our
While space scientists renew the hunt for a living planet, understanding of Earth and its the living systems.
Earth science has launched the grandest study ever con- Ecological principles were laid down only a few
ceived of the only living planet we know, our home planet decades ago with the 1929 publication of the book by
Earth. This study is truly one at a planetary scale involving Vernadsky.[l]. Ecology is the science of how the Earth’s
programs and people from around the world and techno- vegetation and animals assemble into organized internally
logies and modeling barely envisioned just 25 years ago. competing systems interacting within environmental con-
Earth startlingly differs from our solar system neighbors straints. The co-evolution of ecosystems with the environ-
because of the presence and power of life, life which ment provides many clues to our future. Today, for the first
influences virtually every system on Earth. Biospheric time, satellites can measure in a routine way some key pro-
processes on the land, in the coastal zone and in the open perties of ecosystems. These observations are enabling the
ocean exert an influence on Earth’s climate system and prediction of a number of important processes: land use,
climate, in turn, exerts a strong effect on the biosphere and land cover, parts of the carbon and water budgets, and
how it is structured and functions. The biosphere, and life in carbon exchange with aquatic systems. But, the required
general, depend to a great extent on the presence of liquid satellite observations needed is far from complete. Just to
water. Changes in climate as well as changes in the bio- permit a knowledgeable analysis of how the biosphere,
sphere are beginning to affect many aspects of the Earth’s water cycle and the climate system interact with an
hydrologic systems, in particular the delivery of one of the assessment of the influences of human actions demands
smallest fractions, fresh water. These interactions have a much more than is currently planned. Further, a more robust
new and complicating force, the transformational power of satellite program is required to address the manner in which
the growing human population and spirit. And, ultimately, this knowledge can be used to sustain support for all of
how these changes influence the fate and health of the Earth’s living systems, including humans. The long lead
human population is itself compelling. time for satellite programs means the low priority currently
To a great extent, the space agencies have pursued being afforded to advanced remote sensing for biospheric
an old and familiar object, the climate system. From the measurements will stretch the time needed to gain a
earliest days of space observations, Earth’s weather and complete global understanding of this interaction.
climate systems have focused the attention of agencies and While the biological systems of the open ocean and
the public. And, still today, to a large extent the central the coastal zone are vital to understand and predict, the
focus of the space-based global science programs are availability of fresh water is a growing international and
concentrated on the climate system. The focus is different in policy concern. As Matthews [4] articulates so clearly,
the International Geosphere Biosphere Programme, a found- resources will become an increasingly important part of
ing program of the study of global change. While climate future national security policy, with the access to and
effects and influences are clearly stated, there is a greater maintenance of fresh water supplies one of the most urgent.
balance between geospheric and biospheric concerns. One Mirroring the growth of human population and technology,
of the net effects is a loss of priority in the space camp for human demands for fresh water for agriculture and
observations needed for a fuller study of the biosphere. household uses has been growing dramatically these last 50
This paper focuses on biosphere-climate interac- years. Climate change and global warming can alter the
tions including the influences of human activities. Recog- patterns of precipitation delivery, timing, state and quantity
nizing this is only one aspect of biospheric processes, this in ways that are likely to exacerbate fresh water supplies.
places an emphasis of those biogeochemical processes that Impoundments and diversions are a supply solution with
have a profound effect on numerous other aspects of the their own consequences, including the diversion of silt away
biosphere and the services it provides, services which are from the coastal environments as well as the total amount of
critical to sustaining life on Earth. And, the paper will focus fresh water to mix with salt water. The cleansing of water is
on the various scientific aspects of assessing the availability a function of the ecosystem in the contributing watersheds.
of fresh water, including its sensitivity to climate variance The effects of human manipulation of terrestrial ecosystems
and land use changes. Finally, this paper hopes to emphasize worldwide has impacts on fresh water quality and amount
the potential role that greatly expanded space observations that are not well understood. And, the control of fresh water
systems has important effects on the biological systems in
wetlands, streams, lakes and rivers that depend on uncertainties in climate projections.” One of the long-term
evolutionary adaptations to the characteristics of these questions of the USGCRP Changing Ecosystems program
systems. Lastly, human interactions with fresh water element is “how do natural and human-induced changes in
organisms can have profound human health implications. the environment interact to affect the structure, functioning,
Many vectors of infectious disease, such as malaria, and services of ecosystems at a range of spatial and
schistosomiasis, cholera and more have a critical link to the temporal scales, including those functions that can in turn
patterns and condition of fresh water systems. influence regional and global climate.”
The National Science Foundation of the U.S. has a
n.
CURREN T PLANS (NEXT DECADE) research program originally called the Freshwater Initiative
There is quite a bit of consensus among international to initiate research on many aspects of fresh water hydro-
programs on research priorities for terrestrial ecosystems, logy, watershed health, and freshwater ecology. The
the coastal zone, and the open ocean. A significant portion USGCRP Global Water Cycle Program Element lists these
of these objectives concern the interactions of the structure focus areas: (1) the effects of large-scale changes in land use
and function of ecosystems with the climate system and and climate on the capacity of societies to provide adequate
changes in it, and the added complications of the human supplies of clean water; and, (2)h ow natural processes and
dimensions. For example, the objectives of long-term pro- human activities influence the distribution and quality of
grams of the International Geosphere Biosphere Programme water within the Earth system and to what extent the resul-
(IGBP) address this question including Global Climate and tant changes are predictable. The USCCRP reiterates these,
Terrestrial Ecosystems (GCTE), Global Environmental adding concern about the movement of sediments, biogeo-
Change and Food Systems (GECaFS), and Biospheric chemical and toxic subtances, and nutrient transport. These
Aspects of the Hydrological Cycle (BAHC). Recently, programs stress the need for research to inform policy
IGBP initiated the Integrated Land Ecosystem-Atmosphere debates and enter decision processes for water management.
Processes Study (ILEAPS) whose goals is “to provide IGBP recently completed the Biospheric Aspects
understanding of how interacting physical, chemical and of the Hydrologic Cycle, integrating parts into the ILEAPS
biological processes transport and transform energy and and Global Energy and Water Cycle Experiment (GEWEX)
matter through the land-atmosphere interface.” The second of the World Climate Research Program. Much of the
phase of IGBP’s Land Ocean Interactions in the Coastal research was concentrated on the water balance and role of
Zone (LOICZ) Program addresses five themes: (l), river vegetation in regulating that balance.
basins and human dimensions; (2), coastal development and The European community, while largely in agree-
change: Implications for landsea use; (3), fate and trans- ment with the biosphere-climate interactions as discussed in
formation of materials in coastal and shelf waters; (4), NASA’s 2030 vision, has three important areas of diver-
towards system sustainability and resource management; gence. First, what is the role of agricultural lands and not
and, (9,v ulnerability of coastal systems and human safety. just semi-natural vegetation, in the study of biosphere/
The IGBP maintains other studies of the ocean including the climate interactions? Remote sensing has a role to play at
Joint Global Ocean Flux Study concerned with the fluxes of the scale of the field and farm where environmental changes
materials and energy between the ocean and the atmosphere. in space and time are relatively small, ground data are
The United States Global Change Research plentiful and environmental understanding is already strong.
Program (www. usecm.eov, Changing Ecosystems chapter), Increasingly, however, it is being used at the regional to
as well as the U.S. Climate Change Research Program global scale where environmental changes in space and time
(USCCRP), is focused on climate with substantial attention are relatively large, ground data are sparse and environ-
on biosphere interactions. Under USGCRP, regarding the mental understanding is non-existent to poor [3]. At the
reduction of uncertainties in climate prediction, the field to farm scale remotely sensed data are often useful but
sensitivity to unresolved ocean processes is of particular at the regional to global scale they can often be the only data
note. “Because of computer resolution, none of the current source and so are vital. This facility to provide internally
coupled climate models resolve the small ocean eddies (with consistent synoptic data at a range of scales has given agri-
horizontal scales of tens of kilometers) that constitute the cultural remote sensing a major r61e in answering two of the
dominant scale of oceanic variability. These eddies are largest (and interlinked) questions of our time: ‘How does
thought to play a substantial role in regulating oceanic heat our planet work?’ (Le., how does the Earth system function,
transport (via boundary currents) and heat and carbon how is it changing and what are the consequences for life on
storage by regu-lating transport to deep waters. A series of Earth? [5])a nd ‘whither sustainable agriculture?’ (Le., how
eddy-resolving global ocean sensitivity studies are required do we invent a future in which food security is achievable
to assess how well the parameterization of in current climate for all in an environmentally stable way?[2]).
models portray the ocean’s sensitivity to forcing.” This Second, there is an uncertainty about our ability to
planning document says “climate sensitivity is a measure of produce a law-like Earth System Model. A vision of the
the climate’s response to a unit change in radiative forcing Earth Science Enterprise is long term prediction. Such
due, for example, to changing atmospheric concentrations of predictions could include the effect of climate change on
greenhouse gases. It accounts for a major part of the crop yield, insect populations and storm frequency at some
place and time in the future. Such predictions would be productivity have shown a world-wide trend of increasing
need-driven and would necessitate a change in approach. length of growing season’ above 40 degrees N lat. A global
While prediction is linked epistemologically and historically Landsat data base for quantitative assessment of land cover
to science it is not essential and is just becoming a part of has been created. Models of ecological and bio-geochemical
the biologicalEarth science tradition that characterizes cycling have been established that use remote-ly sensed
much agricultural/environmental research. This raises parameters. A fire occurrence product is posted daily from
conceptual difficulties for formulating and promoting an Terra MODIS data. Global ocean chlorophyll and sea
Earth system modeling agenda. The lay/ political audience surface temperature are being assembled from two satellites,
who ultimately support such research do so in the hope that SeaWiFS and Terra MODIS. These data are being used in
piece by piece we can understand how our planet works and models of open ocean carbon exchange.
when we know then we will know what it will do many Over the next ten years, emphasis will shift to
years hence. However, the Earth is complex, every rela- quantifying the seasonal and interannual variations in the
tionship is dependent on external influences, so that long- state of carbon sources and sinks including the coastal ocean
term predictions defy testing [I]. Thus, this research may be and the Southern Ocean. A new satellite, the Orbital Carbon
unlikely to result in law-like predictions. The emphasis is Observatory, will be launched to measure atmospheric
more likely to be on the use of model-derived estimates with profiles of C02 as a constraint on carbon budgets. Carbon
uncertainties [8, IO] within a need-driven technological assimilation models will be expanded to incorporate new
approach (NASA, 2002).and third, most importantly, the understanding of tropical ecosystems and to couple models
importance of sustainable development as a political vehicle with ocean and atmospheric processes (teleconnec-tions).
for Earth observation developments is paramount. The remote sensing of ecosystems will focus on
Both the IGBP and the USGCRF’ explicitly state identification and characterization of plant species
the role of space observations in achieving a global view of functional groups and physiological state for the land, algal
biosphere-climate interactions. For the United States, the blooms and carbon sequestration for marine ecosystems,
agency charged with providing the satellite observations is and forecasts of how ecosystems will respond to multiple
largely NASA. NASA is in the midst of launching the Earth stressors. And, repeated Landsat inventories will help to
Observing System (EOS) to provide a comprehensive data determine the trends in land use change, its causes and the
set of climate relevant variables. The priorities of NASA’s trajectories of response, and the consequences for carbon
Earth Science Enterprise have been concentrated on climate storage and sequestration. Much of this work is aimed at
change and solid Earthhatural hazards research (NASA, providing scientifically sound information for policy setting
2000). This will remain the focus for the next ten years as and for decision support systems to implement policy and
NASA works with its public and commercial partners in the other landlocean management objectives.
U.S. and internationally to provide the first long term data Freshwater systems:
base of 24 key parameters. The program is organized to get While one of the focus areas of the NASA program is the
answers to questions in six specific focus areas: (a) How can water cycle, the ultimate aim of this research is not to
predictions of climate variability and change be improved? determine the regional distribution of fresh water
(b) How will future changes in atmospheric composition availability. Instead it focuses on the role of water and
affect ozone, climate, and air quality? (c) How will carbon energy in the global climate system with aims to improve
cycle dynamics and terrestrial and marine ecosystems the prediction and measurement of precipitation,
change in the future? (d) How will water and energy cycle evaporation rates and so forth. A few groups have used
dynamics change in the future? (e) How can weather digital terrain model data to assemble systems to map
forecast duration and reliability be improved? and (0H ow hydrologic patterns down to small watersheds. The
can our knowledge of Earth surface change be used to prediction of water yield from vegetated watersheds has
predict and mitigate natural hazards? been successful from small catchments to very large river
systems. In general, the uses of remote sensing to
HI. NEAR TERM SCIENCE PROGRAMS characterize fresh water yield and quality, to forecast
Terrestrial and Marine Ecosystems: drought or flooding, to assess effects of changes in water
The ten year U.S. research program in ecosystems stresses flow volumes on fisheries and other aquatic systems is still
the carbon exchange dynamics of North America’s terres- largely undeveloped.
trial ecosystems and the open ocean. While NASA’s bio-
sphere programs are linked with those of the National IV. A DECADAL VIEW
Science Foundation and other U.S. agencies. The recent Looking out to 2030, will the present suite of satellite
NASA program has made substantial progress. A long-term sensors and research foci be sufficient to answer the
observational program has been developed to generate questions of how the biosphere and the climate system
“climate quality” information on ecosystems, primary pro- interact, what the availability of fresh water will be, and
ductivity, and carbon properties (e.g., ocean color, veg index what the influences will be from human actions? Probably
and land cover). Various satellite data driven analyses of the not. By early in the next decade, the science understanding
major seasonal and interannual variations in terrestrial of the carbon cycle will be greatly improved but it will still
lack critical measurements. Certainly net primary produc- adapted ecosystems. Hillslopes denuded of vegetation have
tion will be further along, but probably not, net ecosystem dramatically reduced capability to absorb rainfall, so that
production in which there is an explicit estimation of below- large mass flows can follow fires, clogging reservoirs and
ground respiration and maybe not, maintenance respiration. rivers, and reducing water quality. Current sensors are
There will be an enhanced global understanding of COz and incapable of measuring the most important properties of
water vapor exchange and (2% production and consump- fire, those with predictive power, even though these sensors
tion; but not other important trace gases: N20, NO, CO, can provide a rough estimate of fire occurrence.
NMHC, VOCs, and NH3. What biogeochemical processes The coastal zone has been largely neglected in
regulate these fluxes? Are these processes measurable by satellite planning. Sensors optimized for the open ocean
remote sensing and how much do human actions affect have limited utility in the shallower and often turbid waters
them? And, some progress can be expected on estimating of the coastal zone, a marine system closely coupled to the
precipitation and some components of the water cycle. land. These two ecological domains do share some common
One of the most evident effects of human activity unmet measurement needs, namely, mixed layer depth,
is the transformation of the landscape into uses almost nutrient fields, salinity, and physiolog-ical state. Though a
exclusively for the benefit of humankind. At present we can number of organizations have stated their intention to
lay down an historical record of land cover and try to infer launch satellites to monitor the coastal zone, as of 2003,
land use. But we are not well prepared to predict the course none have succeeded (Peterson et al., 2003).
of ecosystem restoration or the trajectory of response, nor The new or additional measurement requirements
the possibilities that an ecosystem will enter a new and for the biosphere are listed in table 1. Though there is
stable state resistant to restoration. And, what will be the discussion of some of the space technology to make these
consequences of these changed landscapes and the measurements and even some low Technology Readiness
ecosystem services they are supposed to provide for the Level space experiments (notably, the Hyperion
generation of fresh water supplies? hyperspectral imaging spectrometer on EO-1); NASA does
Another event as old as the ages is fire, a force now not have a coherent plan to accomplish the difficult suite of
dominated by humans today with tremendous transforma- measurements described. Commercial companies are now
tion power. Fires produce substantial though poorly under- providing some high spatial resolution observations. And,
stood fluxes of gases and particulates into the troposphere; most of these measurements have been demonstrated from
and can lead to permanent change in ecosystem structure airborne platforms, though even those rarely are optimized
and function. It is also an agent for beneficial change in fire- for specific biological phenomena.
Tab1
Measurements Frequency Technology Needs
OCEANS
Mixed layer depth, wind fields, salinity Daily Active sensors image through
clouds, lidar sensors
Nutrient fields (N, Si, Fe), aerosol deposition, Weekly Passive sensors
hnctional groups
COASTAL ZONE
Colored dissolved organic matter; Chlorophyll and Daily-Weekly Hyperspectral (35 0-900nm) (also:
other pigments; Functional groups; Bathymetry radiometry)
and bottom reflectance; Nutrient concentration (N,
Si, Fe, P)
Physiological state (fluorescence) Daily Space-based passive fluorometer
Or excitement/emission fluorometer
ignm, pigmen
.
J
Table 2 lists measurement requirements for fresh water most challenging will be soil moisture, how to assess soil
assessment. Most of the required measurements are not moisture on a continuous basis down to the rooting depth of
planned nor do they have priority, except those associated most plants, about one meter. The only plans going forward
with natural hazards (sea ice thickness, ice sheet thickness, today are a combination of in situ sampling and remote
snow pack and ice sheet topographic change). One of the sensing for some form of extrapolation.
Table 2. New measurements for Fresh Water Availabilitv
I Ice sheet topographic change 1 <I year J 1-10 km I 1 cm height
New Modeline Required
Gross primary production models of the open atmosphere, they are now based too heavily on correlates to
ocean are based on absorption of photosynthetically active NPP. Modeling of life cycle community structure, based on
radiation in the photic zone and on the sea surface remote sensing data, is less well developed and eventually
temperature. The future models will include functional must be coupled with the ecophysiological models. Future
groups with different rates of efficiency, mixed layer depth, community models will be needed to predict the trajectories
nutrient fields (N, Si, Fe), and aerosol deposition. Carbon of ecosystem response to change, including climatic, land
sequestration to the deep ocean is based on knowledge of use, multiple stressors, species invasions and so forth.
ocean heat transport and circulation patterns. Future Radiative transfer models must be improved to enable
modeling capabilities must integrate mixed layer depth to forward prediction of ecosystem variables from the remote
elucidate the trophic levels of fish and microbiotic species. sensing signals. Such models are needed for not only the
Once in the coastal zone, the spatial resolution of many properties of intact and healthy ecosystems, but for all of the
processes decreases. This zone is subject to episodic altered and disturbed states caused by natural and human
discharge events from the land, which can change the color induced causes including fire behavior. As these models
of the waters and their clarity. Models will be needed of mature and are tested against calibrated data, the models
nutrient redistribution and hypersaline flows. Improvements should allow researchers to better assess the consequences
in bio-optical and radiation transport must be improved, of human interactions: fires, land conversions, grazing,
considering the possibility of bottom reflectance signals, over-utilization, soil degradation, selective and complete
Case 2 waters, and riverine inputs. harvesting, acidic precipitation, as well as climate variation.
Ecopyhysiological models of terrestrial ecosystems In the end, once such models are integrated with other
are improving, on track to predict net primary production components of the Earth system model and further
and related indices of carbon exchange based on remotely intelligence is added on ecosystem services, the modeling
sensed variables. These models are based on short-term suite might be ready to address, in conjunction with the
processes and while they are being used to predict the greatly enlarged satellite data set, to address numerous
production of a host of biogenic gases to and from the practical questions in the terrestrial biosphere.
Table 3. Summary of short term prediction goals enabled by an Earth System Model in 2030. The prediction goals listed below
illustrate the improvements extending from the present capabilities towards those expected, circa 2030.
Today 2010 2030
Availability of Water
First measurements of some Global precipitation Global precipitation, H20,
components of the global measurements: Global evaporation, ice sheet extent,
hydrological cycle: Precipitation, atmospheric water vapor quantitative precipitation
Ice Sheets, SST. measurements forecasts 1 year out.
Allocation of fresh water to mul- First order estimates of fresh Modeling of fresh water produc-
tiple uses poorly understood with water allocation and storage tion, regional distribution and
remote sensing .Hydrologic yield Prediction of the hydro-logical shortages. Modeling of ecosystem
yield and water budgets of processes that produce fresh
understood and modeled regional to large watersheds water and affect water quality
1 Biosphere-climate Interactions
Prediction of high resolution,
Observations of “climate quality” Carbon sources and sinks for
monthly biosphere-atmosphere
ecosystem variables allow North America for carbon
exchange of gases, aerosols and
relating net primary production management decisions based on
energy by oceans, coastal zone,
with carbon balance. reduced uncertainties
and terrestrial biosphere
Predictive understanding of the
First-order characterization of Effects of land use change and
natural and human-induced
annual biogeochemical cycling biomass recovery on carbon
regulatory controls on biospheric
and biospheric processes for balance with carbon pools
processes (climate variability,
carbon in open ocean and assessed; and, accurate
biogeochemical cycles, soil loss,
terrestrial models based on measurement of carbon exchange
hydrology, radiation and land-
remote sensing data and pools for the coastal zone
ocean margins)
Knowledge of statistical Forecasting of ecosystem Capacity to forecast the human
teleconnections between climate response to climate and weather influences on the biosphere-
variability and indices and variability on interannual and atmosphere exchange and
ecosystem responses. biogeochemical cycles.
longer time scales.
Predictive, fully interactive bio-
Carbon process and carbon
sphere modeling at fine space1
Coarse resolution, global net management modeling and
time scales responsing to climate
primary production modeling for forecasting capability that is
variation and human effects (pub-
terrestrial and open ocean ecosystem specific and accounts
lic health, productivity, biological
ecosystems. for disturbance processes (fire
invasions, disaster monitoring,
and land use to first order).
and ecosystem services)
CONCLUSIONS [2] Cartwright, N. ed. (2002) The Big Questions in Science.
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