Issue 103:2 of Journal of Ecology will be online very soon. The Editor’s Choice paper for this issue is Early human impact (5000–3000 BC) affects mountain forest dynamics in the Alps by Schwörer et al. One of Journal of Ecology’s Editors, Amy Austin, has written a commentary about the paper below.

Editor’s Choice 103:2

When we think about human impact on the landscape, visions of deforestation in the Amazon, conversion of grasslands for crop cultivation, or even urbanization of rural areas with sprawling housing developments, often come to mind.  But the truth of the matter is that we, as human beings, have been modifying the natural landscape for thousands of years, and in some places much more intensively than others. The Editor’s Choice paper for this issue of the Journal of Ecology (103:2) explores the effects of human activity on forest biodiversity in the European Alps, but the time frame is not what one might expect – humans were altering biodiversity in these forests more than 5000 years ago!

The alpine Lake Iffigsee (2065 m asl.) in the Swiss Alps

And what did the humans do?  They burned and cleared the forest, and then burned some more and then grazed their animals. Moreover, all of this happened long before industrial civilization took hold of Europe.  These dramatic land-use changes resulted in alterations in the dominant vegetation, from Abies alba (silver fir), a fire-sensitive species, to broad scale expansion of Picea abies (Norway spruce) between 5000 and 3000 years ago. While simultaneous climate changes were happening, Schwörer et al. were able to link fire frequency and extent, resulting from human activity, to the expansion of P. abies in the palaeoecological record.

Coring platform on Lake Iffigsee that was used to retrieve the sediment cores.

How did they discover this?  A combination of approaches, including sediment cores for pollen and microscopic charcoal analysis, macrofossils, and radiocarbon dating of vegetation remains, with intensive sampling in two different locations in the Northern Swiss Alps, was used.  The question that comes to mind is, as with many studies exploring human impact, how can we be sure it was humans and not climatic variability that caused these shifts?  What this study presents is a step forward in the empirical demonstration of human impact. Due to the number of other studies in the region examining climatic change and vegetation distribution (Heiri et al., 2003), the authors were able to show that shifting treeline at the upper elevation site was due to human clearing and fire, rather than natural responses to regional climatic variation.  Other studies have evaluated the importance of large herbivores in determining forest openness and vegetation structure in lowland Europe (Mitchell, 2005; Sandom et al., 2014), but this was the first studies to show how human activity related to pastoralism resulted in detectable changes in forest community composition. The authors even went a step further, suggesting that based on their analysis, moderate human activity in the form of grazing and controlled fires could counteract effects of climate change, and keep silver fir from invading the alpine grasslands as global temperatures rise.

Lake Lauenensee (1382 m asl.)

This study is being published at a time when there is a renewed interest in understanding and using palaeoecological changes, both to establish the magnitude of human-environment interactions in the recent past, but also to use this information as a tool for predictions of human activity in the future. This application of palaeoecological tools was highlighted as priority in a recent review in Journal of Ecology that focuses on 50 key questions for the discipline (Seddon et al., 2014). For this reason, it is a timely and interesting contribution. Take a closer look!

Amy Austin

Editor, Journal of Ecology

References 

Heiri, O., Lotter, A. F., Hausmann, S. & Kienast, F. (2003) A chironomid-based Holocene summer air temperature reconstruction from the Swiss Alps. Holocene, 13, 477-484.

Mitchell, F. J. G. (2005) How open were European primeval forests? Hypothesis testing using palaeoecological data. Journal of Ecology, 93, 168-177.

Sandom, C. J., Ejrnaes, R., Hansen, M. D. D. & Svenning, J. C. (2014) High herbivore density associated with vegetation diversity in interglacial ecosystems. Proceedings of the National Academy of Sciences of the United States of America, 111, 4162-4167.

Seddon, A. W. R., Mackay, A. W., Baker, A. G., Birks, H. J. B., Breman, E., Buck, C. E., Ellis, E. C., Froyd, C. A., Gill, J. L., Gillson, L., Johnson, E. A., Jones, V. J., Juggins, S., Macias-Fauria, M., Mills, K., Morris, J. L., Nogués-Bravo, D., Punyasena, S. W., Roland, T. P., Tanentzap, A. J., Willis, K. J., Aberhan, M., van Asperen, E. N., Austin, W. E. N., Battarbee, R. W., Bhagwat, S., Belanger, C. L., Bennett, K. D., Birks, H. H., Bronk Ramsey, C., Brooks, S. J., de Bruyn, M., Butler, P. G., Chambers, F. M., Clarke, S. J., Davies, A. L., Dearing, J. A., Ezard, T. H. G., Feurdean, A., Flower, R. J., Gell, P., Hausmann, S., Hogan, E. J., Hopkins, M. J., Jeffers, E. S., Korhola, A. A., Marchant, R., Kiefer, T., Lamentowicz, M., Larocque-Tobler, I., López-Merino, L., Liow, L. H., McGowan, S., Miller, J. H., Montoya, E., Morton, O., Nogué, S., Onoufriou, C., Boush, L. P., Rodriguez-Sanchez, F., Rose, N. L., Sayer, C. D., Shaw, H. E., Payne, R., Simpson, G., Sohar, K., Whitehouse, N. J., Williams, J. W. & Witkowski, A. (2014) Looking forward through the past: Identification of 50 priority research questions in palaeoecology. Journal of Ecology, 102, 256-267.