Past vegetation and land-use of the páramo in southern Ecuador

Background/Question/Methods

Ecuador is a country of very high biodiversity, long cultural history and very different landscapes. However, not much research has been devoted to it so far. Being a developing country, the use of land is increasing at a high rate, as well as its population and their economic needs. It is, therefore, important and urgent to understand the ecosystems present in Ecuador, their natural variability and the impact humans could have, as a support for decision makers in developing suitable management techniques that preserve natural vegetation and the life quality of the people.

For this purpose, we use palaeoecological techniques to better understand the vegetation that would be present under natural conditions and to see what impact humans have had since the beginning of the Holocene. We studied a new high-altitude site, the infilled lake Laguna Vendada at 3640 m asl, lying in the southern part of Ecuador. We especially focussed on treeline fluctuations and forest dynamics, so we selected this site lying above the actual treeline but within the potential reach of forest. We studied pollen, microscopic charcoal and macrofossils. The age-depth model was built with 11 C¹⁴-dated samples from terrestrial macrofossils. 

Results/Conclusions

We found several vegetational shifts during the last ca. 18’200 years (calibrated). Pollen and macrofossils show that especially around the mid-Holocene (7000 to 3000 years ago), forests of Polylepis, Weinmannia and Asteraceae trees were reaching the study site and were generally more widely distributed than today. Indications for human transformation of the landscape are apparent since about 8000 years ago, when there was a marked increase in charcoal and dung-inhabiting spores. A major decline of forests and treeline lowering below the study site is apparent around 1000 years ago, coinciding with unambiguous signs of intensified land use in the region in the form of the first occurrence of Zea mays pollen and peaks in charcoal and dung-inhabiting spores.

In conclusion, forests would today be much more wide-spread if it wasn’t for the influence of man. We have clear evidence that grasslands are not the climax vegetation up to ca. 3800 m asl, where they dominate today and only small, isolated patches of forests are found. In contrary to the European Alps, where it is well known that treeline was significantly lowered by man, this is still subject of debate in South America.