by Tom Bulford
Posted 28th February 2017
Let’s start this week with a nice picture:
Source: © Derek Ramsey
This is the monarch butterfly, a great traveller. Every year these fly from Canada and the United States to spend the winter in the forests of Mexico.
On the way they pause to lay their eggs on the Asclepias syriaca, appropriately known as the butterfly flower. The larvae eat the leaves of the plant for a couple of weeks and then turn into butterflies.
The Americans love these winged adventurers, so imagine their horror when they heard that GM crops were destroying them.
In 1999 a study published in Nature magazine found that larvae that fed on leaves sprinkled with the pollen of genetically modified maize tended to die. The outcry against the agricultural industry is still going on. ‘Monsanto and its cronies are beating up an even more innocuous set of victims: beautiful, defenseless monarch butterflies,’ howls one protestor.
But the story is far from simple and it aptly illustrates the difficulties of assessing GM farming.
In the experiment, researchers sprinkled upon the butterfly flower leaves the pollen of Bt maize – that is, maize into which has been introduced a gene derived from the bacterium Bacillus thuringiensis.
This causes it to express a protein that is poisonous to certain pests, including butterflies, and in this case it killed some of them. But did the experiment actually reflect reality in the field?
For this to happen the butterfly flowers must be sufficiently close to the Bt maize to be coated in pollen, and they must be in this condition at the time when the passing butterflies are laying their eggs.
After taking account of these and a few other factors, a more thorough analysis demonstrated that only 0.2% of monarch butterflies could be in danger.
As a research paper from the Belgian Life Sciences Institute VIB explains, the effect of GM, or for that matter any other form of commercial farming upon the natural environment, is extremely complex. I think that plant science is a great investment theme.
I am on the look-out for other companies that are applying biotechnology in the pursuit of more and better food. But the subject generates plenty of heat, not least from the organic foods industry which has a vested interest in trashing anything it can depict as impure.
The fight for more food
It would be lovely to think that we could just rely upon bountiful nature to keep us fed. But plants are in a constant battle against other living organisms such as bacteria, fungi and parasites (so called ‘biotic stress’), as well as their environment of soil, climate etc (‘abiotic stress’). They have developed their own coping mechanisms, such as growing thorns or producing lectin that is poisonous to insects.
But this battleground limits natural crop yields. So one way to satisfy the appetite of the increasing global population is to simply cultivate more and more land each year. But that means cutting down the precious rain forests to make room and nobody thinks that is a good idea.
The alternative is to make land more productive, something we achieved in the latter half of the 20th century thanks to the Green Revolution, a combination of better seeds, irrigation and above all chemical fertilizers.
This dramatically increased crop yields, but it did not come without a cost. Not all of the nutrients of fertilizer are taken up by the plants. Some of it runs off the land. This causes algae to proliferate and coat the surface of rivers, denying sunlight and thus life to anything below.
Just about anything that we do for good intentions has a downside.
Take ploughing for example. What could possibly be wrong with this rustic tradition?
Farmers like to turn the soil to loosen it up and bury weeds below the surface. But this can dry out the land, while the wind can pick up loose soil and blow it away. Consider the dangers of introducing foreign plants and animals.
On Christmas Day 1859 the Victorian Acclimatisation Society thought it would be a nice idea to release 24 rabbits into the wild. Today millions of rabbits cause countless damage to Australia’s flora and fauna and cost farmers a fortune.
Also in the ‘good idea at the time’ category was the kudzu plant. This was introduced from Asia to the USA in the late 19th century to provide shade to front porches and courtyards. Today this rampant and indestructible plant is everywhere and is called ‘the vine that ate the south.’ Here is a scene from Georgia:
Everything in the natural world is in a constant battle for survival. It is highly destructive and mankind has always been in a battle to tame it. The latest weapon is genetic modification, which means carefully and deliberately altering the DNA of a plant so that it will behave differently.
While GM crops have gained widespread acceptance around the world, the EU still bans them, a stance that is increasingly out of step with practice elsewhere.
In a previous report VIB concluded that ‘The scientific facts regarding food safety are overwhelming. Hundreds of studies, strict risk analyses, stringent authorization procedures and continuous follow-up show that GM technology is safe and that the currently authorized GM crops are just as safe as their non-GM counterparts.’
Its conclusion on the impact of GM crops on the environment is more nuanced. ‘Just like crops with specific (genetically engineered) traits, insect-resistant, drought-tolerant, and virus-resistant crops all have direct and indirect effects on the environment. These effects can be either positive or negative but in most cases they will have both positive and negative elements. It is therefore crucial to conduct the risk assessment on a case-by-case basis and to evaluate the environmental impact for the approval for cultivation on the basis of a cost/benefit analysis. In other words: in comparison with the advantages of a certain crop, what is the acceptable and unacceptable impact on the environment?‘
The interaction of nature is so complex that you cannot interfere without some consequences and you must judge any innovation not against raw, unfettered nature, but against other man-made alternatives.
Today GM crops are dominated by maize, soya and cotton and strains that have been genetically engineered to make them resistant to weed-killers and resistant to insects (Bt crops). To ward off the the bollworm cotton has been heavily sprayed with insecticide. The switch to Bt cotton is reckoned to have cut 230 million kgs from insecticide use since 1996.
Reducing insecticide use is clearly a good thing. However when plants themselves are genetically engineered to kill insects we have to ask whether they kill only those insects that pose a threat – ‘target organisms’ – or whether they also kill ‘non-target organisms’.
And then there are the secondary effects. The insects that we deliberately kill might themselves be useful predators of other species, or they could be the chosen food for birds.
A Chinese study on the impact of Bt cotton found that the absence of insecticides allowed ladybirds, lacewings and spiders to survive, and these natural predators then spread to surrounding fields where they controlled other pests.
Self-sabotage from the EU
There is much emotion around GM, but the facts often fail to support the popular supposition. Take the plight of the honey bee, another popular and useful insect.
In Northern Europe its numbers have been in decline. Could this be due to intereaction with Bt crops? No – because no Bt or other GM crops are allowed to be grown Northern Europe. Furthermore Bt proteins interact with a particular receptor in the wall of an insect’s gut.
Bees do not have this particular antenna, and laboratory experiments have shown they suffer no ill effects from Bt.
And yet the EU retains its ban on the cultivation of GM crops – although it is happy to allow them to be imported for animal fodder or used as food ingredients – and doubters remain.
Is it possible that pollen from GM plants could be carried to non-GM, wild, plants and, through sexual reproduction, carried down into subsequent generations – so-called ‘gene flow’?
Yes, they could. Is it possible that articial genes could spontaneously jump from one plant to another, or even to a totally different species, – known as ‘horizontal transfer.’ Again the answer is yes. If herbicide resistant crops allow for limitless spraying of weed-killers, could those weeds develop resistance? Again the answer is yes. Weeds that are tolerant of the the major killer glyphosate have started to emerge.
Could insects adapt to become immune to Bt crops? Yes, the corn rootworm and the cotton bollworm have done so.
So farmers have to ratchet up the fight. They have to rotate their crops more often. They have to allow a minimum distance between fields of GM crops and non-GM. And the designers of GM crops must make them more sophisticated so that they their counteraction of insects or herbicides is more powerful.
Where will this escalating battle between man and nature end? The prospect can seem terrifying. But to lay this at the door of moden GM crops is foolish. Traditional cross-breeding is simply another, and rather laborious and inaccurate, method of genetic engineering. Plants naturally develop resistance to assailants and pollen has always been carried on the wind. Fundamentally modern genetic engineering speeds up natural processes, although it does introduce one new element.
This is the ability to introduce genes across species, for instance introducing genes from fish to plants to make a Camelina plant than produces omega-3 oils. As with all other manifestations of biotechnology, plant science is a rapidly developing commercial endeavour.