LBA-EUSTACH
Summary
Significant changes related to human activities are occurring in Amazonia which could have global effects on the carbon balance, the
concentrations of greenhouse gases and aerosol particles, and on the oxidising power of the atmosphere. Present scientific knowledge is
inadequate to assess these changes and to determine their impacts on global change processes with the required degree of reliability. This
presents a serious drawback for formulating possible outreach of the European Environmental and Climate Change policies.
The Amazon basin constitutes a large global store of carbon which exchanges with the atmosphere. This exchange is influenced by changes
in land use and in relation to variations in climate and atmospheric chemistry. Both types of change introduce uncertainties in the global
carbon balance and both may influence the carbon dioxide concentration of the atmosphere and thus interact with the climate system. Forest
clearing and agricultural development in tropical forests are often cited as a large net source of CO2 to the atmosphere, with a net release
estimated at 25-40% of the net release of CO2 from burning of fossil fuels. The experimental basis for quantitative estimates of the source
strength is weak, however. Mature forests have been assumed to exist in a steady state, but this assumption has never been checked over long
time periods and at a sufficiently large number of measurement sites. Recent short-term measurements in Amazonia indicate that undisturbed
forests may be a net CO2 sink. Moreover, reconversion of abandoned farmland to secondary forest presents a considerable, but as yet unquantified
CO2 sink.
Global atmospheric concentrations of N2O and CH4 have increased dramatically since pre-industrial times. The Amazonian tropical forest
presents a significant source for these greenhouse gases, and it is widely believed to dominate current natural sources for both N2O and CH4.
However, regional net emissions are not defined quantitatively, and the responses of emission rates to climate change or to forest clearing and
associated agricultural development, land abandonment, and ecological succession, are not well understood.
The tropical troposphere is responsible for about 70% of the global atmospheric oxidation of long-lived gases including CH4, CO, HCFCs, and
CH3Br, since the world's highest concentrations of OH are found there. Considerable uncertainty attaches to estimates of photochemical rates,
however, because concentrations and sources of NOx, reactive hydrocarbons, and CO are not well-characterised. The forest soil and canopy are
sources of NOx and hydrocarbons, respectively, and sinks for ozone, but our knowledge of the corresponding fluxes is poor.
Reactive species - NOx, CO, and hydrocarbons - may be exported from Amazonia to the global environment. Deep convection is a major
mechanism for ventilation of the Amazon atmosphere. Reactive species such as NOx may thus be pumped to the upper troposphere where they have
long lifetimes and hence large-scale effects on global atmosphere. However, the mass fluxes associated with convective processes are not well
quantified. Lightning associated with deep convection is thought to represent a major global source of NOx, which can lead to substantial ozone
production, but current estimates of this source vary by more than one order of magnitude.
Amazonia is one of the major direct sources of aerosols (primarily organic) to the global atmosphere. In addition, NH3 emitted from
vegetation and soils can modify the content and phase of the atmospheric aerosol. The size and elemental composition of aerosol particles are
important variables that influence their role as cloud condensation nuclei. Although aerosols and NH3 are efficiently scavenged by
precipitation, export of only a small fraction could make a major contribution to aerosol budgets of the free troposphere.
To address most of these pressing questions, an international research initiative, called The Large Scale Biosphere-Atmosphere Experiment
in Amazonia (LBA) is planned to take place in the Amazon over 1997-2003. LBA is a multidisciplinary research effort, which has been jointly
designed by Brazilian, European and North-American research communities in response to the world-wide concern about the fate of tropical rain
forest and about the global implications of the changes, which the Amazon region has been undergoing. Moreover, the LBA-initiative is a direct
response to the Climate Convention, which requires contributions to the global inventory of greenhouse gases.
The EUSTACH-LBA research project aims to contribute to LBA-initiative by focusing on following two overarching questions with global and
European relevance:
What is the contribution of Amazonia to the global atmospheric carbon balance?
What is the contribution of Amazonia to the global atmospheric budgets of:
radiatively active trace gases (H2O, CO2, CH4, N2O, O3) and aerosol particles?
other trace gases (NOx, NMHC's - esp. VOCs) which are chemically reactive in the global tropospheric ozone cycle ?
Furthermore, the project aims to contribute to understanding and quantification of the role of anthropogenic and natural processes in the
tropics which have been shown to have global impacts and which may therefore alter the composition of the atmosphere over Europe. Moreover,
information on trace gas fluxes and carbon stocks is required by Brazil under the terms of the Climate Convention, and is likely to influence
national policy on land use, with possible global implications for conservation, biodiversity and economy. The EUSTACH-LBA project intends to
broaden the scientific knowledge and data base on which the outreach of European Environmental and Climate Change policies can be assessed.
Objectives and Goals
The Main Objectives of EUSTACH-LBA focuses on the contribution of Amazonia to
the global atmospheric carbon balance
the global atmospheric budgets of radiatively and chemically active trace gases and aerosol particles.
The Goals of the project are:
to quantify the diurnal seasonal and interannual dynamics of CO2, water and energy at three selected sites in the Amazon
Basin by long term measurements
to understand the basic characteristics and spatial variability of CO2, water and energy fluxes across the Amazon basin by
applying state of the art modelling techniques
to quantify the diurnal and seasonal dynamics of concentrations and fluxes of radiatively active trace gases (N2O, CH4) and
aerosol particles
to understand the direct and indirect radiative effect of aerosols from the Amazon basin by interpretive modelling
to quantify the diurnal and seasonal dynamics of concentration and exchange of Volatile Organic Compounds (VOC), O3 and NOx
at three selected sites in the Amazon basin
to assess the role of anthropogenic and biogenic trace gases of the Amazon basin to the (local and regional) ozone
budget/photochemistry and to the global environment
to assess the validity of flux measurement devices used in the project
