Wednesday, 30 January 2013

GM CROPS PART 3: What have GM crops done so far?

Other articles in this series:
Part 1: What are GM crops?
Part 2: Why do we need to improve our crops? What's wrong with the way they are now?

What have GM crops done so far?

Farmers have been growing GM crops since 1994 and they are now grown in 29 different countries. Most of the GM crops currently being grown are modified in one of three ways - they are either herbicide tolerant, insect resistant, or both. This article will explain what these things are and what they have achieved. I will then briefly introduce some of the other GM crops that have been grown.

If you like graphs and want to know more about the history and current status of GM crops around the world, I thoroughly recommend these slides.

Herbicide tolerant crops
When crops are grown in fields they have to compete with other plants (weeds) for the things that they need (water, soil nutrients, sunlight). This is a big problem for farmers because it means that the crops produce less food than they would if there were no weeds competing with them.

Farmers have a number of methods for dealing with weeds. Before the crop is planted, the field can be ploughed to destroy weeds. Once the crop is growing, the farmer can go into the field and remove weeds by hand. The general word used to describe mechanical methods such as these is 'tillage'. Another option is to spray the field with herbicides (chemicals that kill plants). Some herbicides are 'specific', meaning that they only kill certain types of plant, so the crop itself is unharmed.

However, all of these methods have their downsides. Tillage disturbs the soil, which causes greenhouse gasses to be released and results in soil being removed by the wind and rain. It is also time consuming and requires a lot of work. Herbicides pollute the environment, and the use of specific herbicides means that many different herbicides have to be used to make sure that all the different types of weed are killed. Also, herbicides are expensive, especially if you have to buy many different specific ones. As I mentioned in part II, many of the world's poorest farmers cannot afford herbicides.

Not all herbicides are specific. There are some that kill almost all types of plant. These are known as 'broad-spectrum' herbicides. Of course, the problem with using them is that they would also kill the crop. This is where GM comes in. Some plants and some bacteria have genes that tell them how to survive the broad-spectrum herbicides. These genes can be transferred to a crop, making it resistant to the herbicide. GM crops that have been created in this way are known as 'herbicide tolerant crops'. A farmer who grows herbicide-tolerant crops can spray their fields with broad-spectrum herbicides safe in the knowledge that the crop will be unharmed, while almost all weeds will be killed.

Farmers have been growing herbicide-tolerant crops for about 16 years now and it has had three main impacts:

Firstly, it has meant that weeds are killed more effectively. This means that more food is produced per unit of land and farmers no longer have to use mechanical methods such as ploughing which release greenhouse gasses and lead to soil degradation.

Secondly, it has caused farmers to switch from using many different specific herbicides to using just one of the broad-spectrum herbicides. Not only does this save the farmer money, it also benefits the environment because the commonly used broad-spectrum herbicides are less damaging to the environment than most specific ones.

Thirdly, the use of broad-spectrum herbicides means that less herbicide has to be used, because one spray of herbicide kills almost all of the weeds. Research shows that in the 12 years from 1996 to 2008, the use of HT crops caused a 5% reduction in the amount of herbicide used worldwide on cotton, soybean, maize and canola. This benefits the farmer because they spend less money on herbicide and less time spraying it, and the environment because less herbicide is released.

Insect resistant crops
Another problem that farmers face is insects eating their crops. One way to deal with this is to spray crops with insecticides (chemicals that kill insects).

However, there are a number of downsides to this approach. Many insects (such as the corn borer) are able to dig their way inside plants and lay their eggs there. Since insecticides are only sprayed onto the outside of the plant, the insects on the inside are not affected. Also, insecticides can be washed away by rain (which can lead to contamination of rivers). Also, although it is usually only one or two types of insects that are eating the crop, many insecticides are very general and kill lots of different types of insects (including natural enemies of the target insects). Insecticides are generally quite expensive and many of the world's poorest farmers cannot afford them. Poor farmers who can afford them often spray them onto the crops by hand. This means that the farmer comes into contact with a large amount of insecticide and poisonings are common in countries such as India and China.

There is a soil bacterium known as 'Bt' which has a special set of genes. Each of these genes tells it how to make one particular protein, and each of these proteins is poisonous to one specific type of insect. It is possible to take one (or more) of these genes and transfer it into a crop plant. This results in a 'Bt crop', which is able to produce its own insect poison. So far, Bt genes have mostly been used in cotton and maize and it has had many benefits.

Since the insect poison is constantly produced by the plant itself throughout the whole of the plant, there is no risk of it being washed away and it works inside the plant as well as outside. This means that the plant is better protected so more cotton is produced per field1. Secondly, since each Bt protein is only poisonous to one particular type of insect, there is no harm to other insects2 and there is no harm to the people who eat it or the farmers who grow it. Thirdly, there is no need for the farmer to buy or spray insecticide. This saves the farmer money3, prevents farmer poisonings4, and reduces the amount of insecticide released into the environment5.

What other GM crops are being grown?
Almost all of the GM crops that are currently being grown are plants that have been modified in one or both of the ways discussed above. However, there are a few other GM crops being grown in relatively small amounts. For a full list, see the slides I mentioned in the introduction, but here I will just mention one type that I think is quite interesting: the virus-resistant crops.

Just like animals, plants can be affected by viruses. It is possible to protect plants from viruses by transferring a harmless gene from the virus to the plant. This tells the plant how to produce a harmless protein that the virus usually produces. The plant's immune system then trains itself to recognise the protein, so that if it is attacked by the virus the plant will be able to recognise it quickly and destroy it. Papaya that has been modified in this way is grown in the USA and has been credited with saving the Hawaiian papaya industry.

PART 4: What could GM crops do in the future? (coming soon)
There are a lot of new GM crops that have been developed and are going to start being grown in the next few years. Most of these are very different to the ones currently being grown and often address different problems. Part 4 will introduce you to these new GM crops and what they could achieve.

Herbicide-tolerant crops
Bt crops
The impacts that GM crops have had so far

1 Huang and co-workers, 2002 (table 3)↩(return to article)

2 Lu and co-workers, 2012 analysed twenty years worth of data on the number of different types of insects in fields in northern China. They found that the introduction of Bt cotton over the last 16 years has led to a decrease in the number of aphids (which eat crops) and an increase in the number of spiders, ladybirds and lacewings (which eat aphids). They found that the presence of these aphid-eaters also protects nearby fields of non-GM cotton.↩(return to article)

3 Huang and co-workers, 2002 (table 5)↩(return to article)

4 Huang and co-workers, 2002 (table 6)↩(return to article)

5 Huang and co-workers, 2002 (table 4)↩(return to article)

Monday, 21 January 2013

GM CROPS PART 2: Why do we need to improve our crops? What's wrong with the way they are now?

Other articles in this series:
Part 1: What are GM crops?
Part 3: What have GM crops done so far?

Why do we need to improve our crops? What's wrong with the way they are now?

We need to produce more food. While it is true that the world currently produces enough food to feed everyone on Earth, this will not be the case for long if we do not improve our crops. By the year 2050, world population will have risen from its current level of around 7 billion to around 9 billion (an increase of about 30%). If our ability to produce food does not increase then we will not be able to feed these people.

Although we are currently producing enough food to feed everyone, a large chunk of the world's population is starving. This is because rich countries are producing more food than they need, while poor countries are not able to produce enough food. One solution might be for the rich countries to donate their extra food to the poor countries, but there are obvious problems with this strategy. Surely it would be better to give people in poor countries the ability to produce more food for themselves? One of the reasons that poor countries cannot produce enough food is that their farmers cannot afford the large amounts of fertilisers, weed-killers and insecticides that are currently needed to produce large amounts of food.

Hunger isn't the only problem that we face. Many of the world's poorest people suffer from what are called 'nutrient deficiencies'. This means that their diet does not contain enough of certain things (like vitamins, iron and zinc) that are needed to live a healthy life. This is often because their diet mainly consists of one crop, such as rice, and this crop does not contain all of the things that are needed to be healthy. This often means that these people do not develop properly and have weak immune systems. Many of these people live in parts of the world where they do not have access to the medicine needed to treat infections, so having a weak immune system is a serious problem. (Read more about this here).

There are other factors that mean we will need to produce more food in the future. Firstly, some poor countries are becoming less poor. This is clearly a good thing, but it does mean that people in those countries will start wanting to eat more of a mixed diet than they currently do, including more meat. Meat production requires a lot more land than growing crops (partly because the animals have to be fed and that food comes from crops). This is land that we do not have available. Also, meat production is much worse for the environment that growing crops (read more about the environmental impact of eating meat here). Another problem is global warming. Although it might seem like warmer weather should help with growing crops, the reality is that climate change will make it much harder to produce food in the future.

The way that we currently produce food causes a lot of damage to the environment. Fertilisers, weed-killers and insecticides cause serious pollution. Their use also contributes massively to our global greenhouse gas emissions. But we can't just stop using them. We absolutely rely on them for food production. If we stopped using them then a lot more people would be starving. Fortunately, there are ways of using them more effectively so that smaller amounts are needed. However, the ideal solution would be if we had plants that produced large amounts of food without any need for these inputs.

Unfortunately, food production has another impact on the environment that is worse than anything I have mentioned so far. Land that is used for farming is much, much, much worse at absorbing carbon dioxide (one of the major greenhouse gasses that cause global warming) than land that is left to grow naturally. In fact, research has shown that the increased use of fertiliser, weed-killers and insecticides in the past 40 years has actually had an overall positive effect on the environment, because it meant that we could produce more food per field, which meant that we needed less farmland than we otherwise would have.

So what can GM crops do to help with these problems? Well actually they have done quite a lot already and have the potential to do a lot more in the future. Find out more in Part III (coming soon). 

GM CROPS PART 1: What are GM crops?

Other articles in this series:
Part 2: Why do we need to improve our crops? What's wrong with the way they are now?
Part 3: What have GM crops done so far?

What are GM crops?
GM stands for 'genetically modified'. This post explains what that means.

Every living thing contains a set of instructions that tell it how to be itself. These instructions are called 'genes'. An elephant has a set of genes that tell it how to be an elephant. An oak tree has a set of genes that tell it how to be an oak tree. A bacterium has a set of genes that tell it how to be a bacterium.

Most living things have thousands of genes (a human has about twenty thousand) and each gene is the instruction for doing one particular thing. If you compared the genes in two different living things (a cat and a sunflower, say), you would find that there are quite a lot of genes that they have in common. This is because there are many things that they both need to do. For example, a cat and a sunflower both need to burn food to release energy. In order for a living thing to burn food it needs to produce a set of tiny machines called 'enzymes'. Therefore the cat and the sunflower both have genes that tell them how to produce these machines. However, there are obviously also a lot of differences between a cat and a sunflower, so they don't have all the same genes. A cat has genes that tell it how to make eyes, a sunflower doesn't. A sunflower has genes that tell it how to make petals, a cat doesn't. It is a living thing's complete set of genes that make it what it is. A living thing's complete set of genes is called its 'genome'. 

All of the genes (instructions) that exist are written in the same language (the language of DNA). This means that if a gene is transferred from one living thing to another it will still work. This happens naturally all the time because viruses and bacteria are able to physically move genes from one living thing to another. For example, bacteria regularly pass useful genes on to each other (such as genes that allow them to survive antibiotics). It isn't just tiny bacteria that share genes though, all living things do it. For example, it has recently been discovered that a quarter of the cow genome was transferred over from a snake!

Scientists have found their own ways of moving genes from one living thing to another. This means that we can add genes to crops (the plants that produce our food). We can give a crop a new gene that we have taken from another living thing. This new gene tells the crop how to do something that it couldn't do before. The crop is now called a 'genetically modified (GM) crop' because it has had its genome modified. 

Click here to read Part II. It's called 'Why do we need to improve our crops? What's wrong with the way they are now?'

Tuesday, 15 January 2013

Coming Soon: 'Genetically modified crops, good or bad? My thoughts.'

When I first applied to Cambridge University, they sent me the following question and told me that I would be expected to discuss it at interview:
'What are the benefits and potential risks of genetic modification?'
It was a question that I had wanted to know the answer to for a while, so I was glad to have something to motivate me to do some reading about it. I had heard about genetic modification, and genetically modified crops in particular, on the news, but didn't feel very well informed. All I really knew was that GM crops were something that scientists had made for farmers and that a lot of people were opposed to them.

So I did some reading. I found out about the different types of genetically modified crops, why they have been developed, what advantages they have and what concerns people have about them. I didn't exactly become an expert, but I felt informed enough to have an interesting discussion on the topic. I was looking forward to that part of the interview.

When the interview did roll around, the interviewers made it clear early on that they didn't want to discuss the advantages and disadvantages of genetic modification. Instead, they wanted to quiz me on my understanding of the technical aspects of how scientists genetically modify things in the lab. I don't really mind though. Being set that question started me on the path that I am still following today. I am still trying to improve and refine my answer the question they set me.

The good news is that they accepted me and I spent three years studying science in Cambridge. In the third year I specialised in plant sciences, which gave me plenty of opportunity to learn more about genetic modification. I learnt new things about genetically modified crops, I met some of the scientists who develop them and I read more about some of the risks that might be associated with them.

Since graduating, I have started this blog. I try to write about a wide range of plant and food related topics, but the issue of GM does seem to come up quite a lot. For a while now, I have been aware of the fact that although I mention GM a lot on here, and I generally seem to give the impression that I am in favour of it, I have never explicitly explained my stance on the issue.

Then, a few weeks ago, a friend posed the following question to me: "What are the main good things about GM crops and what are the main legitimate concerns about their use?" Apparently he recently came close to disagreeing with a stranger on a bus who was bad-mouthing GM crops, but then realised that he didn't really know much about it so kept quiet (he is clearly very brave, I would never do that). So he has turned to me for answers (which is fair enough, I do talk about crop science quite a bit).

Up until now, I haven't really felt too worried about the fact that I haven't gotten round to explaining my position on GM crops. This is because I know that no-one actually reads my blog posts (friends keep telling me that they opened the page but then "it all got sciency" so they closed it. I'm trying to work on this.). But, now that someone has actually asked me directly, I feel like now is the time to write about it, because I know that at least one person will read it.

In late 2008, Cambridge University asked me a question that motivated me to read about something that I had been meaning to read about for ages. Now, my friend has asked me a question that has motivated me to write about something that I have been meaning to write about for ages.

In the next day or two, I will put up a post explaining my stance on GM crops. I will try to make it as readable as possible and avoid scientific terms as much as possible. Hopefully it will be something that I could show to the me of four year ago and save him a lot of time. [Update: in the end I decided to do a series of posts called 'GM Crops'. Click here for part one. (Also, it definitely took me more than a day or two).]


P.S. Yeah, I know. It is quite weird that I have posted a post about an upcoming post. I did consider adding the second post to the bottom of this one, but that would mean that it had a 600 word introduction, which makes me feel uneasy. Sorry if you read this hoping that it would contain anything other than self-indulgent anecdote. 


Hello to all my regular readers! Since you don't exist, you probably won't have noticed that I haven't posted here for quite some time. This is because I decided that I was going to 'take December off'. I realise now that this was a very poor decision because it meant that I started the new year with a list of articles that I wanted to read so long that it has taken me until mid-January to get through them (I use google reader).

The good news is that I am now back and have a big old stack of links for you. A few of them are things that I haven't actually read yet myself but since they look interesting and I don't want to leave the blog dormant for even longer while I get round to reading them, I have decided to just post them anyway. Enjoy!

  • If you only follow one of these links, follow this one. It is a video of a talk given by the journalist and environmental activist Mark Lynas to the recent Oxford Farming Conference. In the talk, he apologises for the years that he spent campaigning against GM crops, says that he has now 'discovered science' and explains why he is now in favour of GM. Not only it is amazing that this has happened, it is also a really well-delivered talk, in which he explains his reasons very clearly. 
  • A nice video from Kew Gardens about the Millenium Seed Bank Partnership. 
  • 'Redrawing the Tree of Lifeis a fantastic piece by Carl Zimmer about the way in which scientists have been rethinking evolution since the days of Darwin. 
  • Karl from the Biofortified Blog guides us through a recent talk he gave about the benefits and risks of genetically engineered crops.
  • 'GM crops increase biodiversity, study finds'. This is obviously very exciting news, but I think the headline should probably be more like 'one particular type of GM crop has been shown to increase biodiversity in one particular region of China'. If you're wondering how this is possible, the explanation is that this crop (BT cotton) requires less insecticide to protect it, so there is less damage to local insects. For more detail, see my post on BT crops or this 'BT cotton Q&A' document. 

Friday, 30 November 2012


  • The genome of bread wheat has been sequenced. Not only is this an impressive feat (the wheat genome is a very large and complicated thing which arose through the fusion of three other genomes) it is also very promising in terms of feeding the world. About 20% of human calories come from wheat, and knowing the genome will make it easier to improve the crop in the future.