Earth's Deep Secret

Two years after we were told trees communicated with each other, and were 'social', scientists at a geophysical meeting in Washington confirm abundant life at depths of up to 5 km.

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Today, Thursday, December 13, marks the penultimate day of the five-day 'Fall Meeting' in Washington of the American Geophysical Union (AGU). This annual conference is the world's largest Earth and space-science meeting, with well over 20,000 scientists attending.

Despite the size and importance of this organisation, its annual conference does not normally feature in newspapers around the world. This year has been very different.

At the AGU conference, the Deep Carbon Observatory (DCO) announced that it had uncovered a diverse ecosystem in the crust, up to 5 km below the surface. DCO is a global community of more than 1,000 scientists from 50 countries on a ten-year quest to understand the quantities, forms and origins of carbon in Earth. That might sound dull but, in the ninth year of the investigation, the DCO's scientists have uncovered a wilderness in the crust that rivals the world's most diverse ecosystems.

For many years, drillers have observed microbial cells from deep holes, and have attributed them to contamination. Not so, apparently; the DCO told the AGU conference that over two-thirds of the planet's microbial life actually exists underground. Indeed, the microbes in the crust represent an ecosystem twice the size of the oceans. In places the microbes are eating plant matter that has been buried for millions of years. It is, according to the DCO scientists, a huge component of the world's biomass.

The investigation has involved drilling 2.5 km into the seafloor, and sampling microbes from deep mines and boreholes more than 5 km deep (the deepest that life has been found). DCO told delegates that these deep microbes are often very different from their surface cousins, with life cycles on near-geologic timescales, dining in some cases on nothing more than energy from rocks.

In terms of surprise, and mild uncertainty for the mining industry, this week's announcements rival those of two years ago when we were told that trees communicated with each other.

You might recall the publication in September 2016 of 'The Hidden Life of Trees: What They Feel, How They Communicate' by Peter Wohlleben. The book was a publishing sensation, and reflected intense research that had been ongoing since the turn of the century.  

Scientific studies, conducted at well-respected universities, had confirmed that trees were alert, sophisticated and even social. The research showed that trees of the same species are communal, and will often form alliances with trees of other species. Forest trees were able to evolve, and lived in co-operative, interdependent relationships, maintained by communication and a collective intelligence similar to that of an insect colony. Mr Wohlleben called it the 'wood-wide web'.

Trees, we were told, send distress signals about drought and disease, or insect attacks. Scientists call this a mycorrhizal network; fine, hair-like root tips that join together with microscopic fungal filaments to form the basic links of a network. A study from Leipzig University and the German Centre for Integrative Biodiversity Research showed that trees can recognise the taste of deer saliva. When being eaten, trees are able to generate chemicals that make their leaves unpleasant to taste. Trees also know the difference if a branch was being broken by a human, and generate substances to heal the wound.

All rather perplexing. In 2016 there was concern that miners on surface operations might need to talk nicely to the trees, now it is the turn of operators underground to worry about new life forms. 

Chris Hinde

Chief Commentator, Mining Beacon

Previously editorial director of Mining Journal, and more recently head of S&P Global Market Intelligence's metals and mining team, Chris is now Mining Beacon's editor-in-chief and lead commentator. He posts two blogs every week, one on Monday reviewing market conditions over the prior week, and a second on Thursday looking at issues on the global mining scene. There is also a quarterly blog on business opportunities in the sector.