SELECTIVE SCIENTIFIC EVIDENCE

  • Written by Andrew Davis
  • Posted on Oct 19, 2020
  • Articles

All can agree that policy should be based on sound scientific evidence.  That has been emphasised consistently by the Prime Minister during the Covid-19 pandemic in recent months.  But what constitutes sound scientific evidence and who should we believe when the experts disagree?

At one extreme is ‘fake news’, much loved by President Trump.  It may be totally false information, rumour or innuendo spread with malicious intent but, in his case, it may just be an opinion with which he disagrees regardless of the evidence.  More common, and increasingly so, is the practice of picking particular pieces of evidence from a wide range, often conflicting, and ignoring the rest in an attempt to prove a specific point.

One example of this is the campaign to get the agricultural herbicide glyphosate banned.  There have been numerous studies that find the chemical safe to use but some, more recent, suggest that it may be carcinogenic.  How can regulators decide when the scientific evidence is contradictory?  That leads on to the debate about risk and hazard.  Many chemicals, including some widely-used medicines, are hazardous in that they may cause damage or even death when taken in very large doses.  But what is the risk of that happening?  Frequently, regulators follow the precautionary principle and take a decision based on potential hazard rather than actual risk.

There are many examples of controversial debates within agriculture and land use that have become increasingly polarised as each side selects evidence that seems to back their case.  The issue of genetic modification and gene editing is prominent among them.  This is a need to define terms, to distinguish between transgenics, where genes from other species are introduced, and sysgenics or gene editing, where the indigenous genes are manipulated without any introduction of foreign material.  It is likely that gene editing will be allowed in this country once we leave the European Union legislative jurisdiction.

A recent report in Farmers Weekly highlights the selective use of evidence in the debate over the culling of badgers in the fight against bovine tuberculosis.  A group of vets, academics and naturalists wrote an open letter to the Prime Minister in early September claiming that the badger cull is ineffective and should be abandoned forthwith.  The Downs Report showed that over the first four year of the cull in Gloucestershire there was significant drop in bovine TB but the letter claimed that this conclusion would have been very different had the sharp rise in the fifth year been taken into account.Another group of vets and an immunologist contested this view in a further open letter to the Prime Minister saying that it was disingenuous.  Their letter claimed that the first group had deliberately ignored evidence from the other nineteen cull zones, all of which showed continued declines in bovine TB.  There was also disputed evidence about the proportion of culled badgers that were infected and the effectiveness of the skin test used in cattle to detect the disease.

Another issue that is debated with more emotion than scientific evaluation is the practice of the rotational burning of heather.  This is carried out on many grouse moors to create a mosaic of heather of different ages to provide a better habitat for many species, including grouse, lapwing, curlew, golden plover and hen harriers.  But some conservationist groups, including the RSPB and CPRE, have warned that ’we’re watching England’s rainforests burn’, demanding that ‘setting fire to the peat’ be banned because it releases vast amounts of carbon dioxide and makes the land more vulnerable to flooding lower down the catchment.

Other groups, including the Scottish Fire and Rescue Service, fundamentally disagree.  Very strict regulation of the practice, which can only be carried out between 1st October and 15th April, ensures that only small patches of old and woody heather are burnt and not the peat beneath.  The relatively small amount of carbon released is more than offset by the sequestration of the re-growing heather.  More importantly, the controlled burning of the old heather reduces the fuel load and likelihood of wildfires in hot dry weather in summer when the peat is likely to catch fire as well.

Recent peer reviewed research by the Game and Wildlife Conservation Trust provides evidence of this, whilst the Scottish Fire and Rescue Service claims that controlled burning of heather is a vital tool in the prevention of wildfires, especially in the context of climate change.

It is the role of campaigners and lobby groups to press Government to legislate or regulate in their interests.  But the selective use of scientific research reduces rather than enhances the credibility of their campaigns.  In many of these controversial debates there is a wealth of scientific evidence, some of it contradictory.  The responsible approach is to review all of these studies and make a judgement based solely on the most credible consensus.