More than half the world's rainforest has been lost to agriculture since the Industrial Revolution. Among the most widespread tropical crops is oil palm (Elaeis guineensis): global production now exceeds 35 million tonnes per year. In Malaysia, for example, 13% of land area is now oil palm plantation, compared with 1% in 1974. There are enormous pressures to increase palm oil production for food, domestic products, and, especially, biofuels. Greater use of palm oil for biofuel production is predicated on the assumption that palm oil is an ''environmentally friendly'' fuel feedstock. Here we show, using measurements and models, that oil palm plantations in Malaysia directly emit more oxides of nitrogen and volatile organic compounds than rainforest. These compounds lead to the production of ground-level ozone (O 3), an air pollutant that damages human health, plants, and materials, reduces crop productivity, and has effects on the Earth's climate. Our measurements show that, at present, O 3 concentrations do not differ significantly over rainforest and adjacent oil palm plantation landscapes. However, our model calculations predict that if concentrations of oxides of nitrogen in Borneo are allowed to reach those currently seen over rural North America and Europe, ground-level O 3 concentrations will reach 100 parts per billion (10 9 ) volume (ppbv) and exceed levels known to be harmful to human health. Our study provides an early warning of the urgent need to develop policies that manage nitrogen emissions if the detrimental effects of palm oil production on air quality and climate are to be avoided. air quality ͉ land use change ͉ sustainable development ͉ biofuel G round-level ozone (O 3 ) is a priority air pollutant that damages human health, plants, and materials, reduces crop productivity, and has direct and indirect effects on the Earth's climate system (1). It is formed in the atmosphere by reactions involving oxides of nitrogen (NO x ) and volatile organic compounds (VOCs) in the presence of sunlight. The terrestrial biosphere is a major source of both these families of trace gases; in fact, the great majority of reactive VOCs globally are of biogenic origin (2). Here we show, using integrated and fully comprehensive measurements of biosphere-to-atmosphere trace gas fluxes and atmospheric composition, together with atmospheric chemistry modeling, that conversion of tropical rainforest to oil palm plantations results in much greater emissions of these reactive trace gases that lead to O 3 formation. Increased NO x emissions will cause severe ground-level O 3 pollution (Ͼ 100 ppbv), but this pollution could be prevented by strict control of emissions of reactive nitrogen species to the atmosphere. Our study shows the importance of quantifying the current and future effects of land use change on air quality when assessing the ''environmental friendliness'' of palm oil and other biofuel crops. Of course, air quality is only a single consideration; in assessing the consequences of biofuel production, effects o...

During June, July and August 2006 five aircraft took part in a campaign over West Africa to observe the aerosol content and chemical composition of the troposphere and lower stratosphere as part of the African Monsoon Multidisciplinary Analysis (AMMA) project. These are the first such measurements in this region during the monsoon period. In addition to providing an overview of the tropospheric composition, this paper provides a description of the measurement strategy (flights performed, instrumental payloads, wing-tip to wing-tip comparisons) and points to some of the important findings discussed in more detail in other papers in this special issue

Abstract. Chemical and meteorological parameters measured on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft during the African Monsoon Multidisciplinary Analysis (AMMA) campaign are presented to show the impact of NO x emissions from recently wetted soils in West Africa. NO emissions from soils have been previously observed in many geographical areas with different types of soil/vegetation cover during small scale studies and have been inferred at large scales from satellite measurements of NO x . This study is the first dedicated to showing the emissions of NO x at an intermediate scale between local surface sites and continental satellite measurements. The measurements reveal pronounced mesoscale variations in NO x concentrations closely linked to spatial patterns of antecedent rainfall. Fluxes required to maintain the NO x concentrations observed by the BAe-146 in a number of cases studies and for a range of assumed OH concentrations (1×10 6 to 1×10 7 molecules cm −3 ) are calculated to be in the range 8.4 to 36.1 ng N m −2 s −1 . These values are comparable to the range of fluxes from 0.5 to 28 ng N m −2 s −1 reported from small scale field studies in a variety of non-nutrient rich tropical and sub-tropical locations reported in the review of Davidson and Kingerlee (1997). The fluxes calculated in the present study have been scaled up to cover the area of the Sahel bounded by 10 to 20 N and 10 E to 20 W giving an estimated emission of 0.03 to 0.30 Tg N from this area for

Abstract. Nitrogen oxide biogenic emissions from soils are driven by soil and environmental parameters. The relationship between these parameters and NO fluxes is highly non linear. A new algorithm, based on a neural network calculation, is used to reproduce the NO biogenic emissions linked to precipitations in the Sahel on the 6 August 2006 during the AMMA campaign. This algorithm has been coupled in the surface scheme of a coupled chemistry dynamics model (MesoNH Chemistry) to estimate the impact of the NO emissions on NO x and O 3 formation in the lower troposphere for this particular episode. Four different simulations on the same domain and at the same period are compared: one with anthropogenic emissions only, one with soil NO emissions from a static inventory, at low time and space resolution, one with NO emissions from neural network, and one with NO from neural network plus lightning NO x . The influence of NO x from lightning is limited to the upper troposphere. The NO emission from soils calculated with neural network responds to changes in soil moisture giving enhanced emissions over the wetted soil, as observed by aircraft measurements after the passing of a convective system. The subsequent enhancement of NO x and ozone is limited to the lowest layers of the atmosphere in modelling, whereas measurements show higher concentrations above 1000 m. The neural network algorithm, applied in the Sahel region for one particular day of the wet season, allows an immediate response of fluxes to environmental parameters, unlike static emission inventories. Stewart et al. (2008) is a companion paper to this one which looks at NO x and ozone concentrations in the boundary layer as measured on a research aircraft, examinesCorrespondence to: C. Delon (claire.delon@aero.obs-mip.fr) how they vary with respect to the soil moisture, as indicated by surface temperature anomalies, and deduces NO x fluxes. In this current paper the model-derived results are compared to the observations and calculated fluxes presented by Stewart et al. (2008).

Abstract. This paper presents measurements of organic aerosols above subtropical West Africa during the wet season using data from the UK Facility for Airborne Atmospheric Measurements (FAAM) aircraft. Measurements of biogenic volatile organic compounds (BVOC) at low altitudes over these subtropical forests were made during the African Monsoon Multidisciplinary Analysis (AMMA) field experiment during July and August 2006 mainly above Benin, Nigeria and Niger. Data from an Aerodyne Quadrupole Aerosol Mass Spectrometer show a median organic aerosol loading of 1.07 µg m −3 over tropical West Africa, which represents the first regionally averaged assessment of organic aerosol mass (OM) in this region during the wet season. This is broadly in agreement with global model predictions based on partitioning schemes, although there are large uncertainties associated with such estimates. In contrast our own calculations based on aerosol yields from isoprene and monoterpenes during chamber studies under represent the OM measured in this region on a comparable scale to the under representations of OM by predictive models in the mid latitudes. As global models rely on similar yield calculations in their global estimates, as our calculations this points to further systematic differences between global model estimates and measurements of SOA, most likely caused by use of incorrect BVOC emission rates. The under predictions of OM by our calculations and those in the mid latitudes employ yields Correspondence to: G. Capes (gerard.capes@manchester.ac.uk) extrapolated from chamber data obtained at higher mass concentrations -more recent yield data for α-pinene obtained at ambient concentrations in a flow through chamber (Shilling et al., 2008) show considerably better agreement with our data.