My occasional series of posts looking back over my career had reached Italy just in time for me to ruminate on the problems that would face Britain were it to leave the single market (see “How to make an ecologist #9”). I did not get so far, in that post, to talk about why we had dragged so much equipment across Europe in the first place.
The project was a European Community (as it then was)-funded project to look at the vegetation history in the period following the last ice age; the standard way to do this is to collect a long core of sediment from the middle of a lake or bog, then to take samples from different depths along this core and examine the types of pollen grains that are present. Because sediments are laid down sequentially over time, changes in the composition of the pollen as you move from the bottom to the top of the core provides a record of how the plants that were producing pollen in the area had changed over that time.
This was the period when global climate change was beginning to be recognised as a serious problem. People had worked out that looking at the insights into vegetation in the past that pollen analysis offered could give many clues about climate at the time. This, in turn, could be used to check the models that were being developed to predict climate change: in effect, if the models can “hindcast” climates that support vegetation known to exist at points in the past, then maybe we will also be able to “forecast” with greater confidence. The problem was that most of the people doing this work were in the moist temperate parts of Europe and North America, where there are plenty of lakes and bogs from which to core. Drier parts of the world, such as the Mediterranean Basin, had fewer lakes, a consequence of which was that there were fewer scientists with an interest in these techniques. This also meant that there were fewer historical benchmarks in this region against which climate models could be tested, and our project set out to fill this gap.
One feature of peninsula Italy is that there are a number of lakes associated with the cones of extinct volcanoes, and this was had already raised the prospect of opportunities to collect cores that would help us understand how vegetation and climate had changed in this reagion. We travelled first to Monte Vulture (photographed above), in the Basilicata region around the “ankle” of Italy, to collect cores from Lago Grande di Monticchio, one of the two lakes inside the crater of the volcano. I included a photograph of us coring in the marsh area beside the lake in my previous post on this subject; the 33 m long core that we collected was passed on to Bill Watts at Trinity College Dublin to continue a study of the lake that started a few years earlier. Subsequent visits by the Durham team and collaborators (after I had moved on) extended this glimpse into the past back to over 100,000 years ago.
The second location that we visited was a small crater lake, Lago di Martignano, just to the north of Rome. We collected this with help from geologists from Edinburgh University who had a “Mackereth” corer. This is a contraption that uses compressed air pumped from a boat to first push the corer into the soft sediments and then to slowly extract the core and bring it to the surface. The final stage, when the core is free from the sediment and filled with compressed air, results in a dramatic emergence of the core, cables, floats and other paraphernalia, which leap into the air above the lake surface before crashing back down. Needless to say, capturing the event on camera is not easy, but everyone tries …
Using a Mackerth-type corer in Lago di Martignano, Lazio, Italy, September 1988. The left hand picture shows the buoy marking the spot where the corer has been lowered, and the cables through which compressed air is pumped; the right hand image shows the corer breaking the surface of the lake once the core has been collected.
That core, from Lago di Martignano, was the one that I worked on for the next year, extracting the pollen with a cocktail of strong chemicals. Our house was burgled during this time and the scene of crime investigator who was investigating to my fingerprints in order to eliminate these from his investigations. He tried several times before telling me to take up a life of crime as I had no fingerprints and was, therefore, undetectable. I attributed this to conditions in the rather basic laboratory that we were using at the time to prepare our samples.
Very roughly, the balance between pollen from trees associated with temperate climates, such as deciduous oak and beech, and pollen from the shrubs typical of the hot dry Mediterranean climate (see pictures below) allowed some insights into the climate that prevailed at the time that the sediment was laid down. In the upper levels of the core, however, we also had to account for the effects of humans, removing trees and planting cereals and, in the process, upsetting the pure climate-driven signal that we were looking for. Unravelling this mix of influences made for an intriguing challenge, and also led to my first serious forays into statistical analyses, performed, in those days, on slow mainframe computers.
Characteristic “maquis” plants, photographed during fieldwork in Italy during 1988. Top left: Erica arborea (tree heather); top right: Pistachia lentiscus (pistachio); bottom left: Rosmarinus officinalis (rosemary); bottom right: Paliurus spina-christi (Jerusalem thorn / crown of thorns).
The method only worked, however, if we could “calibrate” our historical records against modern situations where the climate was already known. The quest for pollen samples from a wide range of climates spilled over into holidays, with a memorable sampling trip during a trip to Jordan in 1989. We drove into the Syrian desert on a dull, overcast day in search of Azraq Oasis, as sediment from the ponds here would have given us an insight into the pollen we might expect in semi-desert conditions. There were more than just scientific reasons for wanting to make this trip: there is a 13th century castle at Azraq, built on the site of an earlier Roman fort. We live close to Hadrian’s Wall and here, at Azraq, we were 4000 kilometres away at the opposite corner of the Roman Empire. The castle is still largely intact and was, in fact, the headquarters for T.E. Lawrence’s operations against the Ottomans during the First World War, and little had changed since he wrote Seven Pillars of Wisdom. I seem to recall that another Lawrence – D.H. this time – was cited in an early draft of the paper that arose from this study. His travel memoir Etruscan Places had some references to the densely-forested landscape that had inhibited Roman soldiers in their forays against the Etrurians. I thought that this corroborated our results; however, it had disappeared from the manuscript before it was submitted, probably for the best. By that stage I was in Nigeria and too far away to fight my corner. But that is jumping ahead …
Qasr Azraq in the Syrian Desert in Jordan, photographed during our visit in spring 1989; the right hand image shows the Bedu custodian demonstrating the stone doors.
Kelly M.G. & Huntley B. (1991). An 11,000-year record of vegetation and environment from Lago di Martignano, Latium, Italy. Journal of Quaternary Science 6: 209-224.