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Ancient DNA and pollen in fossilised urine towers reveal climate change

Rock hyraxes from South Africa use communal latrines which can preserve pollen and stable isotopes for thousands of years. Image Credit: Shutterstock
Rock hyraxes from South Africa use communal latrines which can preserve pollen and stable isotopes for thousands of years. Image Credit: Shutterstock

Fossilised urine from rabbit-like animals called hyraxes could tell scientists how plants and animals may react to future climate change.

According to Dr Brian Chase, of the EU-funded HYRAX project, the urine is probably the strongest fossil evidence that scientists have to work with for the southern African region. That’s because he can get a wide variety of fossils from any one site.

The thing with hyraxes is they always urinate in the exact same place, meaning that over thousands of years it builds up into a fossilised tower called a midden, which can be up to two metres tall.

‘From any piece of the midden sample you can get stable isotopes (forms of elements used for dating, and indicators of past climate and vegetation), ancient DNA, pollen, phytoliths. Each one of these provides part of the picture,’ said Dr Chase, from France’s national research centre CNRS.

‘Not only can you see what happened in terms of climate and vegetation change, but also how these changes are a response to changes in the global climate system. And that’s of very critical importance.’

Dr Chase’s results can be used to improve climate change models which will lead to more accurate predictions of future climates.

Drones

His data-collecting team explores Namibia and South Africa looking for hyrax colonies, and locate the fossilised urine using drones, as hyraxes generally live in cliffs.

To get up to the midden involves abseiling and rock climbing. So reaching a potential site can take a full day, and if the scientists don’t find anything there, it’s a lot of wasted effort.

‘When a day in the field is costing EUR 500, a drone that costs EUR 400 suddenly makes a lot of sense. Fly up, fly back, download the images and look at the movie right away,’ said Dr Chase.

Within the middens, Dr Chase and his team find pieces of pollen which can tell us a lot about vegetation in climates past. This pollen would have stuck to the coats of the hyrax as they roamed the South African grasslands and then been brushed off onto the urine towers. There’s no microbial activity in the middens so the pollen is perfectly preserved.

‘The results that we’ve gotten have just been phenomenal,’ Dr Chase said.

  • Middens are made up of layers of fossilised urine, built up over thousands of years, which can be over 2m tall. Image: Brian Chase
  • Rock hyraxes live in cliffs which can be difficult to get to, meaning it is less labour-intensive to use drones to collect images. Image: Brian Chase
  • Fossilised pollen can tell scientists how plants reacted to climate change in the past. Image: Kathy Willis
  • Driftwood fossils are telling scientists where ice used to be and how it has moved during the Holocene Era. Image: Dr Marc Macias-Fauria.

In Europe too, pollen is shedding light on the past – and illuminating the future. There’s a whole European Pollen Database which collects both fossilised and modern pollen records all across Northern Europe, from Iceland to Russia.

Dr Luke Mander of the EU-funded MioVAT project is using pollen to map how grasslands have evolved over time. He focuses on the grassland pollen of the Miocene Epoch, which stretched from 23 to five million years ago. During this time, grasslands first appeared on earth.

Now, grasses are found in almost all habitats on earth – in fact, there are over 11 000 species of grass.

Future climate change

It’s important that scientists understand as much about vegetation as possible, because many of our medicines, remedies and foods come from plants. Added to that, understanding how past climates operated is essential for theories about future climate change to be formed.

Although Dr Mander’s research focuses specifically on the Miocene, he thinks that there’s potential for researchers to make the link between what happened in the past and what’s happening now.

‘The crucial contribution of the fossil record is the ability to examine the evolutionary process in these times and that gives us a route to thinking about very broad, long-term controls on the composition of vegetation on planet earth,’ he said.

Dr Marc Macias-Fauria, who worked on the EU-funded ECOCHANGE project, agrees. ‘The fossil record provides a unique source of information about what has happened,’ he said.

Like MioVAT, ECOCHANGE studied fossilised pollen. One of its main results was to work out how fossil pollen and ecological modelling can be used together to track climate-related changes in trees.

‘The fossil record provides a unique source of information about what has happened.’ 

Dr Marc Macias-Fauria, University of Oxford, UK

Dr Macias-Fauria’s research also found that factors other than climate alone, such as geology and geomorphology, had a much larger impact on the positioning of many types of plants - including trees on the Rocky Mountain range - than previously thought.

Added to that, ECOCHANGE’s research at the Oxford Long-term Ecology Lab, led by Prof. Kathy Willis, gave scientists a better idea of how species react to changing environments. This is important when constructing climate change models, which try to predict how the planet will react as the earth warms up.

Moving on from ECOCHANGE, Dr Macias-Fauria is now working on driftwood fossils – these fossils, found in the Arctic regions, can tell us how sea ice moved in the past.

‘By analysing these pieces of wood – of which there are thousands in the Arctic, we can start creating a map of where the ice was, and how it was moving over the last ten to twelve thousand years – the Holocene Epoch,’ he said.

European Pollen Database

The European Pollen database is a non-profit database available free-of-charge to the scientific community. It was first set up in the 1980s to provide a structure for archiving, exchanging, and analysing pollen data from throughout Europe.

It holds over 1800 pollen sequences from almost 1500 different sites, which comes to well over one million individual pollen counts.

The database is hosted by the Mediterranean Institute of Marine and Terrestrial Biodiversity and Ecology.

For more information, you can visit their website here: http://www.europeanpollendatabase.net/

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