Ancient fish bones reveal impacts of global warming benea...(he warm Atlantic period (ca. 70003900 BC...)

Global and regional climate models predict that air and sea temperatures will rise by approximately 3C during the next 70100 years. In order to understand some of the processes by which global warming might affect marine fish species near Denmark, researchers have investigated the fish fauna during one of the warmest prehistoric periods (the warm Atlantic period: ca. 70003900 BC).

A total of 108,000 fish bones were identified, and amongst them were bones of many species, for example, anchovy and black sea bream, which we usually consider to be typical of waters much farther south and warmer like the Bay of Biscay and the Mediterranean Sea. When temperatures cooled after the warm period ended, most of these species disappeared from the archaeological record, suggesting that local abundances declined. However, many of those same warm-water species have recently reappeared in waters around Denmark as temperatures have risen in the last 1015 years. The archaeological information can be an indicator of which species may become common as climate change progresses and warms.

There were also thousands of cod bones present together with the warm-water species. That result was surprising because investigators knew that the increase in sea temperatures since the late 1980s to the early 1990s has reduced the survival of young cod in the North Sea. How can these two findings be reconciled? The researchers believe that the difference is due to the much lower fishing pressure in the archaeological period. The message from their work is that sustainable cod populations can be maintained in the North Sea even during the climate change expected in the 21st century, but the fish mortality needs to be lowered.

For further information contact: Inge B. Enghoff, Natural History Museum of Denmark (Zoological Museum), University of Copenhagen; email: