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Tree mortality in tropical moist forests in Australia has been increasing since the mid 1980s. The death rate of trees appears to have doubled over that time period. According to an international team of researchers, the primary cause is drier air in these forests, the consequence of human-induced climate change. According to ecologist David Bauman, a similar process is likely underway in tropical forests on other continents.

Also in the programme: the outbreaks of monkeypox in Europe and North America… Could SARS-CoV-2 infection lingering in the gut be a cause of Long Covid? News of a vaccine against Epstein Barr virus, the cause of mononucleosis, various cancers and multiple sclerosis.

Digging and excavating are bywords for archaeology. But why does history end up deep under our feet?

This question struck CrowdScience listener Sunil in an underground car park. Archaeological remains found during the car park’s construction were displayed in the subterranean stairwells, getting progressively older the deeper he went. How had these treasures become covered in so much soil over the centuries?

CrowdScience visits Lisbon, the capital of Portugal – and home to the above-mentioned multi-storey car park. The city has evidence of human habitation stretching back into prehistory, with remnants of successive civilisations embedded and jumbled up below today’s street level. Why did it all end up like this?

Human behaviour is one factor, but natural processes are at work too. Over at Butser Ancient Farm, an experimental archaeology site in the UK, we explore the myriad forces of nature that cover up – or expose - ancient buildings and artefacts over time.

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Credit: Getty Images