Monitoring biogeographical response to climate change: The potential role of aeropalynology

Abstract

To test models predicting biological reponse to future climate change, it is essential to find climatically-sensitive, easily monitored biological indicators that respond to climate change. Routine monitoring of airborne pollen, now undertaken on a near-global basis, could be adapted for this purpose. Analysis of spatial and seasonal variations in pollen levels in New Zealand suggests that the timing of onset and peak abundance of certain pollen taxa should be explored as possible bio-indicators of climate change. The onset of the airborne grass pollen season during the summer of 1988/89 varied consistently with latitude, and hence temperature, with the season in Southland commencing 8--9 days after Northland. However, these patterns were only apparent after sampling sites were separated into two groups reflecting predominantly urban or rural pollen sources. A less consistent north to south trend was apparent in the frequency of high (30 grains/m3) grass pollen levels, with high levels frequent in North Island localities in November, December and January and in southern localities during December and January. The successive onset of pollen seasons for the principal tree species during the spring-to-early summer warming interval may also be a useful bio-indicator of climate change. As well as assisting forecasts of the onset of the pollinosis season, these biogeographical patterns, reflecting climatic variation with latitude, suggest that routine aeropalynological monitoring might provide early signals of vegetation response to climate change. These conclusions are supported by recent investigations of long-term aeropalynological datasets in Europe that indicate earlier onset of pollen seasons in response to recent global warming.