Reconstructing nutrient cycling in the palaeorecord to assess current global changes Seminar

Human activities have doubled the pre-industrial supply of reactive nitrogen on Earth, and future rates of increase are expected to accelerate. The long-term response of the terrestrial biosphere to this potential fertilization is largely unknown. Here, I present several palaeoecological records from lacustrine sediment cores and tree cores to begin to establish a baseline for 20th century changes in nitrogen cycling. The spatial scales of these records range from local (watershed-level) to global. There is little evidence indicating widespread eutrophication in the past 500 years despite increasing anthropogenic supplies of reactive nitrogen. Non-anthropogenic drivers of nitrogen cycling, especially the carbon status of terrestrial ecosystems, are likely to be essential for understanding which ecosystems are vulnerable to future anthropogenic changes.