Holocene environmental vulnerability in Iberian Peninsula from pollen records: atlantic and mediterranean patterns
by
Santiago Riera
Dept. prehistory, Ancient History and Archaeology. University of Barcelona
Coauthors: Ramon Juia

The Iberian Peninsula is located in a specific climatic zone which covers the latitudinal transition from the Atlantic to the arid Mediterranean. This climatic gradient allows us to analyse the evolution of several propagation patterns and their interrelations as well as the responses of the ecosystems to these changes. This paper presents the results of a new analysis based on the comparison of a large set of pollen sequences and radiocarbon dates covering from 9,000 to 2,000 yr BP.

The numerical treatment allowed us to clearly identify four periods in the 500 yr window with a percentage of event occurrences higher than 40%. When the time window was reduced to 250 yr, six periods of maximum frequency of event occurrence could be differentiated:

1. 7500-8250 BP

2. 7000 BP

3. 6000 BP

4. 4000-4500 BP

5. 3000-3250 BP

6. 2500 BP

The use of this broad time window permits us to identify 4 major periods during the Holocene with a high occurrence of pollen changes. These periods display maximum frequency at: 7500-8500 BP, 6000-6500 BP, 4000-4500 BP and 2500-3500 BP.

Periods of major stability occur at 7000-6500 BP and at 4000-3500 BP in the whole Iberian Peninsula.

The Mediterranean basin was more affected by periods of change (6 on the basis of 250 yr window calculations) than the Atlantic region (3 periods). Mediterranean vegetation is probably more vulnerable to long dry spells.

It should be pointed out that although some periods of change were only documented in the Mediterranean region, the inverse situation did not occur: no periods of high occurrence of pollen change were exclusively recorded in the Atlantic area.

Date received: March 20, 2002