Quantifying Anthropogenic Impacts on Dust Flux and its Interaction with Recipient Ecosystems

Anthropogenic landuse, principally agriculture, has been shown to result in increased dust emissions from susceptible environments in a number of discrete studies. However, until now, there has been no broad-scale assessment of changes in dust emissions associated with human activity. Earth’s surface has undergone a vast transition associated with the conversion of wildlands to agricultural landscapes. This included development of semiarid and arid landscapes, which are highly sensitive to wind erosion, for agriculture. Much of this change occurred in the period between the late 19th and mid-20th Centuries. Therefore, they occurred prior to the beginning of scientific investigation of Earth systems and widespread environmental concern. As a result, empirically quantifying changes to dust emissions is problematic due to a lack of data from this time period, and consequently, the impact of these changes has been underappreciated. However, sedimentary archives, such as ice cores, which record dust flux both before and following widespread landuse change, allow the magnitude of anthropogenic dust emissions to be estimated. In this thesis a global compilation of data from sedimentary archives is presented, that allows an assessment of the change in dust emissions driven by human activity. Results show that globally dust emissions increased by a factor of 2.1 times after the Industrial Revolution (1750 CE). This change coincides with the development of ‘industrial agriculture’ and the colonisation and development of new regions, e.g. Australia. Increases in anthropogenic dust are also shown by data compiled from other study types, such as remote sensing, airborne sediment sampling and meteorological station data. These additional studies, which don’t predate the onset of industrial agriculture, and are more likely to be distorted by short term climate variability, suggest human activity has increased dust emissions by 1.3 to 45 times. Despite the uncertainties in these records and the limited number and spatial availably of sedimentary archive studies (n=25), in combination they nevertheless imply that at least a doubling in dust emissions has occurred during the past ~250 years. The loss of soil associated with this change presents a serious challenge to soil security, while the increased dust load in the atmosphere is likely to have had a recognisable impact on biogeochemical cycles and climate. Consequently, the impact of changes both to, and from, global dust emissions warrants further investigation