Could lemmings be involved in regulating our climate?

November 17, 2011

The mention of lemmings usually evokes images of small rodents throwing themselves off the top of cliffs in acts of mass suicide; however, their reputations might no longer be determined by hearsay as a new report suggests they could be having an intricate effect on the Earth's climate.

The study, published today, 18 November, in IOP Publishing's journal Environmental Research Letters, suggests that lemmings may be maintaining the biomass of certain plants in the Arctic at a time when the greening of this vast area is becoming more noticeable.

When lemmings are excluded from the Arctic environment, the researchers, from the University of Texas at El Paso, observed an increase in certain plant types called lichens and bryophytes; however when the lemmings were present there were surprising increases in grass and sedge - the plant material that lemmings actually feed on.

"Our paper confirms that we really need to be careful attributing the greening of the Arctic to global warming alone. We have shown that lemmings can promote similar greening, through the increase of grasses and sedges, as warming does in Arctic regions where lemmings are present and go through dramatic population cycles," said lead author of the study David Johnson.

The increase of grass and sedge could be due to changes in nutrient availability in soils from the addition of urine and faeces from the lemmings, or by simply reducing competition for space by keeping bryophyte and lichen abundance low, as well as reducing the amount of standing dead grass and sedge litter.

Lemming populations have historically gone through periods of highs and lows, which researchers believe have played a key role in regulating many properties and processes of tundra ecosystems.To measure these effects, the researchers measured plant cover and biomass in 50-year-old lemming exclosures and control plots in the coastal tundra near Barrow, Alaska.

Satellite imagery has already confirmed that Arctic regions are becoming increasingly populated with greenery, such as grasses and shrubs, as increasing temperatures make the areas more habitable.

As the Arctic regions continue to become populated with more plant biomass during the summer months, the effects on the climate could tip either way. Warmer temperatures may allow plants to grow bigger and store more carbon, taking carbon dioxide out of the atmosphere and potentially reducing climate warming.

Conversely, soil decomposition increases with warmer temperatures meaning soil microbes are respiring and releasing carbon into the atmosphere and potentially increasing climate warming.

"We still don't know the relative magnitude of these two feedbacks to warming. A greener landscape may maintain the region as a carbon sink, however higher plant growth in a greener landscape may not be enough to offset losses of carbon from soil microbes. It is plausible that herbivores, in some situations, may provide a mechanism for higher plant growth maintaining these ecosystems as carbon sinks.

"We are not saying that lemmings are causing the greening, because greening is occurring in areas where lemmings don't occur at high densities and we are not sure how lemming populations across the Arctic are themselves responding to warmer conditions. However, it is clear from our study that lemmings, and other herbivores, are more important in some of these Arctic ecosystems than people historically give them credit for," continued Johnson.
-end-
From Friday 18 November, this paper can be downloaded from http://iopscience.iop.org/1748-9326/6/4/045507

Notes to Editors

Contact

1. For further information, a full draft of the journal paper or contact with one of the researchers, contact IOP Press Officer, Michael Bishop:
Tel: 0117 930 1032
E-mail: Michael.bishop@iop.org

Exclusion of brown lemmings reduces vascular plant cover and biomass in arctic coastal tundra: resampling of a 50+ year herbivore exclosure experiment near Barrow, Alaska

2. The published version of the paper 'Exclusion of brown lemmings reduces vascular plant cover and biomass in arctic coastal tundra: resampling of a 50+ year herbivore exclosure experiment near Barrow, Alaska' (D R Johnson, M J Lara, G R Shaver, G O Batzli, J D Shaw and C E Tweedie 2011 Environ. Res. Lett. 6 045507) will be freely available online from Friday 18 November. It will be available at http://iopscience.iop.org/1748-9326/6/4/045507

Environmental Research Letters

3. Environmental Research Letters is an open access journal that covers all of environmental science, providing a coherent and integrated approach including research articles, perspectives and editorials.

IOP Publishing

4. IOP Publishing provides publications through which leading-edge scientific research is distributed worldwide. IOP Publishing is central to the Institute of Physics (IOP), a not-for-profit society. Any financial surplus earned by IOP Publishing goes to support science through the activities of IOP. Beyond our traditional journals programme, we make high-value scientific information easily accessible through an ever-evolving portfolio of community websites, magazines, conference proceedings and a multitude of electronic services. Focused on making the most of new technologies, we're continually improving our electronic interfaces to make it easier for researchers to find exactly what they need, when they need it, in the format that suits them best. Go to http://ioppublishing.org/.

The Institute of Physics

5. The Institute of Physics is a leading scientific society promoting physics and bringing physicists together for the benefit of all.

It has a worldwide membership of around 40 000, comprising physicists from all sectors, as well as those with an interest in physics. It works to advance physics research, application and education; and engages with policymakers and the public to develop awareness and understanding of physics. Its publishing company, IOP Publishing, is a world leader in professional scientific communications. Go to www.iop.org

IOP Publishing

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