A horizon scan of global biological conservation issues for 2024

We present the results of our 15th horizon scan of novel issues that could influence biological conservation in the future. From an initial list of 96 issues, our international panel of scientists and practitioners identified 15 that we consider important for societies worldwide to track and potentially respond to. Issues are novel within conservation or represent a substantial positive or negative step-change with global or regional extents. For example, new sources of hydrogen fuel and changes in deep-sea currents may have profound impacts on marine and terrestrial ecosystems. Technological advances that may be positive include benchtop DNA printers and the industrialisation of approaches that can create high-protein food from air, potentially reducing the pressure on land for food production

On the historic exposure levels of Elemental Carbon from vehicle diesel exhaust based on “diesel smoke” concentrations

Air pollution by diesel traffic became a concern in the UK in the 1950s. Exposure levels were assessed via probing the light absorption of filter samples, which was translated to a mass concentration of “diesel smoke” (DS), based on the results of a measurements in the exhaust of a test diesel engine. We convert these DS values to concentrations of Elemental Carbon (EC), the current proxy for diesel exhaust. In a recent study in the literature and an earlier own investigation a high similarity (R2 = 0.97) was found of the light absorption by aerosol collected in parallel on glass and quartz fibre filters and probed by smoke-stain reflectometers similar to those used historically. For samples on quartz fibre filters the relation between light absorption and EC was taken from recent studies. The shape of the absorption/EC curve is highly similar to the absorption/DS curve, with an equivalency factor of 1.6 ± 20% between DS and EC concentration (expressed according to the EUSAAR2-TOT method). Converted EC concentrations for workday average 24-hr and morning rush hour samples were around 75 and 150 μg m− 3 at the kerbside of the busy London A1 ring-road in 1960. In 1961–1962 the average weekday daytime EC concentration at a traffic island in inner city Fleet Street was 200–250 μg m− 3. Only 45 m into a sidestreet the concentration was an order of magnitude less. At the end of the 1990-ies EC concentrations at the nearby Marylebone Road were around 9 μg m− 3, dropping to 3 μg m− 3 in recent years. In addition, we found the correct factor to convert light absorption to EC mass concentration of samples obtained in the FH62 beta gauge monitors used in Germany in compliance measurements for the national “soot law” preceeding the EU PM10 regulation of 1997

Crystallisation of mixtures of ammonium nitrate, ammonium sulphate and soot

Crystallisation of laboratory aerosols of ammonium nitrate and of internal mixtures of this salt with ammonium sulphate were investigated using humidity controlled nephelometry. The aerosol was produced via nebulizing of solutions and then dried to 25% RH, which is a realistic minimum value for ambient air. Pure ammonium nitrate and aerosols consisting of internal mixtures of ammonium nitrate and ammonium sulphate with a mixing ratio of more than 1.2 did not crystallize, which is in contrast to assumptions that crystallisation of such mixtures occurs in the atmosphere. Addition of realistic amounts of 'soot' did not promote crystallisation. Aerosols with equal ratios of ammonium nitrate to ammonium sulphate crystallized and showed a (first) deliquescence point close to that of ammonium nitrate. Ambient aerosol with a similar mixing ratio behaved similarly. Because the laboratory tests demonstrated that the crystallisation of ammonium nitrate is not promoted by soot but only by the ammonium sulphate, it is concluded that the ambient aerosol particles consisted of internal mixtures of ammonium nitrate and ammonium sulphate

Fate of products of degradation processes: consequences for climatic change

The end products of atmospheric degradation are not only CO2 and H2O but also sulfate and nitrate depending on the chemical composition of the substances which are subject to degradation processes. Atmospheric degradation has thus a direct influence on the radiative balance of the earth not only due to formation of greenhouse gases but also of aerosols. Aerosols of a diameter of 0.1 to 2 micrometer, reflect short wave sunlight very efficiently leading to a radiative forcing which is estimated to be about -0.8 watt per m2 by IPCC. Aerosols also influence the radiative balance by way of cloud formation. If more aerosols are present, clouds are formed with more and smaller droplets and these clouds have a higher albedo and are more stable compared to clouds with larger droplets. Not only sulfate, but also nitrate and polar organic compounds, formed as intermediates in degradation processes, contribute to this direct and indirect aerosol effect. Estimates for the Netherlands indicate a direct effect of -4 watt m-2 and an indirect effect of as large as -5 watt m-2. About one third is caused by sulfates, one third by nitrates and last third by polar organic compounds. This large radiative forcing is obviously non-uniform and depends on local conditions

Radiative forcing due to sulfate aerosols in Europe

Climate effects due to the increasing burden of manmade aerosols are expected to countarct the warming effects due to increasing levels of greenhouse gases by a significant part. Here, we consider the direct effects of sulfate aerosols. The atmospheric lifetime of these aerosols is in the order of a week, depending on meteorological conditions. Hence, their concentratíons show a large variability in space and time. Sulfur emissions lead to the formation of sulfate aerosols. These particles are capable of reflecting solar radiation. In addition to this direct efiect, aerosols may alter the size distribution of cloud droplets and hence the reflectivity of clouds. The total aerosol efiect is not well-known. Uncertainties are largely associeted with estimates of the emissions of the precursors snd with the parameterizations of chemical processes as well as the modelled transports. In addition, uncertainties in the microphysical properties, such as seize distribution and the interactions of aerosols with water vapour and droplets, hamper accurate estimates of the radiative effect