The sediments at the bottom of the sea can provide a window into the past, indicating environmental conditions not only from the sea but washed from terrestrial runoff, as well as preserving the flora and fauna of the time. Scientists access this knowledge by taking exploratory cruises to core the ocean floor, bringing these cores to the surface for examination in laboratories.
One such expedition, reported on The Holocene, the cores were obtained from the Gulf of Saint Eufemia, on the west coast of Calabria, Italy. Knowing the size of the basin where the cores were obtained is important because it helps to identify the spatial distribution where the sediments and inclusions, such as pollen and spores, were obtained; Large basins can draw soil material from hundreds of meters away, providing information on regional vegetation patterns, while small basins are more likely to draw material from the immediate environment and therefore offers a more local picture of plant communities.
Studying the pollen grains and spores preserved in these cores (palynology), researchers from the University of Naples Federico II, Italy, and their colleagues have been able to chart the colonization of Italy by the Greeks and Romans. for the past 5,000 years. To do this, pollen is taken from the sediment (up to a surprising 12,000 grains per gram of material) and examined under a microscope, with 72 species identified.
The results reveal three distinct vegetation phases in the region: dense forest between 5055 and 2700 years before present (BP), forest reduction and drying between 2700 and 2000 BP, and deforestation with intensive agriculture from 790 BP to the present.
These vegetation patterns may be closely related to the communities that lived in the area at the time with the Pre-Protohistoric populations that sought a home in the dense forest. However, they may be starting to see the effects of climate change as the researchers noted three long periods of hundreds of years where plants showed increased drought conditions in the area.
The second phase corresponds to the rise of the Greek (7th to 5th century BC) and Roman (3rd to 2nd century BC) populations in the area, with evidence of a decrease in forest cover, instead replaced by intensification of agriculture based on the preservation of grains and vegetables of the tribe Cichorieae (with familiar members lettuce, chicory and dandelion).
The high abundance of microcharcoal in the sediments compared to the previous phase is a significant indicator of population growth, because it preserves the remains of burning for cooking and heating.
On the other hand, in the last phase, widespread deforestation damaged the soil and increased water flow, which is evidenced by increased sedimentation rates. The authors also noted that during the 6th century AD, the change in the rate of sedimentation was probably linked to the collapse of the Western Roman Empire in the region, with a sudden decrease in land management that meant ruralization. .
This is further supported by the reduction of microcharcoals found in the samples as communities reduce burning activities, as well as the reduction of fir pollen as these trees are cut for timber (a resource that was once well managed by Romans, but saw local exploitation after they left the area).
Combined with archaeological studies of the Mediterranean basin, palynology is an important indicator of vegetation changes as a result of human occupation of the area. The climate in Italy during the last 5,000 years (mid and late Holocene) has been punctuated by successive cooler and drier periods, and therefore it is likely a combination of urbanization and climate change that has affected the plant communities through time and space.
Today, the region experiences many microclimates due to the altitude, with average annual temperatures ranging from 7°C to 16°C. In the mountains, tree populations are dominated by turkey oak and beech, with a small contribution of fir, while pine and oak are found along the coast, next to agricultural land. Palynologists of the future may experience the same combination of climate and human influences on our local landscapes.
Halinka Di Lorenzo et al, A high resolution record of landscape and land use changes over the last 5000 years in western Calabria (S. Eufemia Gulf, southern Tyrrhenian Sea, Italy), The Holocene (2023). DOI: 10.1177/09596836231176487
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Citation: The rise and fall of the Roman empire preserved in pollen (2023, July 10) retrieved 10 July 2023 from https://phys.org/news/2023-07-fall-roman-empire-pollen.html
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