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30 Years later

It was while serving my time on the governments’ Advisory Committee on Pesticides (ACP). It took a year or two to work out that we risk assessed every possible impact for using the particular pesticide that required approval, We looked at impacts, or direct effects, on land, air , water, but especially people. We were asked whether it would be appropriate for GM crops to go through a process similar to the risk assessment we carried out for pesticides. There would be just one difference. Pesticides considered direct effects, while GM would also consider indirect impacts (ie the whole nature of farming may alter to fit the GM requirements). GM approval would need to look at all the changes. Interesting, I thought, I am glad I am not on that Committee; this one is difficult enough.

Then it hit me. Why didn’t I look at both direct and indirect impacts of herbicides together all those years ago? It doesn’t matter (to a soil animal when it is dead) whether the effect is direct or indirect, the animals have gone. No wonder I couldn’t find any real differences of direct effects all those years ago. The main effects are indirect – as that is the whole purpose of herbicides – to kill plants. But the mesofauna that are lost are still lost. They don’t bother whether it is because of direct toxic effects or indirect effects; they are dead. That’s what is important.

Why didn’t I look at the total number of dead and what that said about the state of the soil?

And I would like to have had glyphosate to look at. If the toxicity is not relevant and it is the overall effects which are, then another herbicide having similar overall effects as glyphosate will do (eg Dalapon). But unfortunately I had only looked at the loss from grassland soils, not ploughed fields – where Glyphosate is used.

If Kenneth Mellanby were alive today to ask me the same question, I would now answer it completely differently. Obviously I would include glyphosate in my trials, as this is the herbicide used most widely worldwide. While almost benign in toxicity terms, it has a massive effect on the soils where it is applied. 

I would look at what the loss of decaying plant material is to the overall soil environment, and whether anything moves in to fill the space, or whether it just degrades to look like sand or clay. Clearly there would be widely different results depending on the crops and soils involved.

I had used grass as the starting point and a total herbicide like Dalapon and Glyphosate should get rid of most of the grass. This would be akin to ploughing up in terms of Soil Organic Matter (SOM) loss. While this is significant, it is quite well dealt with – although some people seem to blame the ploughing for loss, it is the lack of grass herbage going back into the soil that it the problem. However, glyphosate is usually used on ploughed fields to keep weeds other than the desired crop from growing. So the issue is the lack of weed herbage going back into the soil.

I would have set up the trail differently and compared ploughed land growing various crops, with different total herbicide treatments to see what the effects were. This would have indicated the damage to soil animals caused by lack of herbage going back to the ground.

This is part of a much wider paradigm shift in our environmental outlook. 30 years ago we were preoccupied with poisons killing us and the environment off - from DDT to PCB and dioxins. Now we are more worried about carbon dioxide rather than carbon monoxide, as the world is over heating and refined carbohydrates rather than additives in food, as we are over eating.

This could be significant and may explain the loss of SOM from our soil in the last 30 years. About 12 – 15% was lost between 1980 – 95, according to the old Soil Survey[2] 

No mention of this statistic was made in the recent DEFRA Soil Strategy for England Supporting Evidence Paper (Sept 09) when talking about soil organic matter decline[3]. 

This loss is often put down to ploughing. But it is unlikely that ploughing alone could explain SOM loss, and even if it did, whether it would explain such a loss when there is no sign of an increase in ploughing during that time. What is more likely is that there has been an increase in total herbicide usage that time. If so this could account for a large increase in CO2 left in the air instead of being utilised by the weeds and their herbage returned to the earth – as Soil carbon. Perhaps in future we will look to our weeds being climate friendly

It should be possible to come to some sort of calculation at the loss of carbon from the soil due to loss of weeds, and what that means in terms of extra carbon dioxide in the atmosphere, and the worldwide contribution this may make to global warming. 

Between 1945 and 1986, the amount of carbon released from UK land tripled. Since 1980, UK soils lost 12-15% carbon of the total carbon in the soil, due mainly to loss from arable lands. This is about 4Million tonnes/yr lost in Greenhouse Gas Emissions. There has been a reduction in GHG emissions from UK agriculture since 1990 of about 14%. 13 mtonnes of C02 estimated to be lost from UK soil each year "Carbon losses from all soils across England and Wales 1978-2003[4]

Countryside Survey of 2007 shows that the carbon loss is only form Arable Soils..Link to Save our Arable Soils

The overall trend seems ominous: the loss of carbon from arable land in England & Wales Soil has been significant. In 15 years, soils with the highest concentrations of carbon - greater than 7%, dropped from 22% of soil to 10% of the total. Source: SSLRC, National Soil Inventory. MAFF (now DEFRA) project quoted in Application of National Sustainable Agriculture Indicators[8]

The most popular reason for the decline is usually given as more ploughing. Certainly the change from grassland to cultivation does make for a big loss of organic matter. But we do not know of studies that have quantified this according to whether there has been an increase in ploughing over last 20 or so years. Consideration should also go into the increased usage of herbicides / weedkillers as they will reduce the contribution of vegetable debris back to the soil.


..to come ...

more details about UK government's position - Where has the Soil Strategy gone? Why do they oppose the EU Soils Directive?. And role of new Global Partnership...And now with Brexit, is there any chance of a NAtional Action Plan?

CAP role...Part of Cross Compliance requirements..

Good Agricultural and Environmental Condition (GAEC) 1 (Soil Protection Review)

Farming Regulation Task Force February 2012 Department for Environment, Food and Rural Affairs ..

7.46 We recommend that Defra changes GAEC 1 to ‘a duty of care’ to protect the soil and to prevent damaging soil erosion, reduce compaction, damage to landscape features and, over the long run, maintain organic matter in mineral soils.

Government Response (not a yes, as they did for 159 of the >200 recommendations)...It is

‘Under consideration’

'We will work with industry to explore the full range of options for the Soil Protection Review (SPR10). We aim to put new arrangements in place by the end of 2013 when the current SPR10 comes to an end. We have already conducted initial analysis to explore how a duty of care for soils could be implemented and believe a duty could be one of several options which could be considered. As part of the review, we will consider how the SPR and other industry schemes can be used in earned recognition. To start the process, we will launch a farmer survey in February 2012 to evaluate the implementation of the SPR10 so far and explore current soil management trends in England.'

Will bring details of this survey here, when it is launched..
Further Questions

These are the questions raised by this revisiting of the earlier work:
Role of weedkillers / herbicides very widespread, esp with the “Herbicide Resistant” GM strains coming in across the world.. What is the loss of carbon in the soil and all its related biodiversity aspect lost with continual total herbicide (eg Dalapon, Glyphosate) use v traditional ploughed land?

Change in emphasis among ecologists and environmentalist from toxic concerns (eg DDT, Dieldrin, Dioxins & PCBs casing ozone depletion) to problems over the very natural chemical – carbon. (There is a similar paradigm shift in nutrition. Similarly concerns over food were often about safety (eg Salmonella, pesticide residues) whereas it is the health effects of consuming too many calories causing obesity and diabetes - again carbon/carbohydrate related. Carbon and carbohydrate counting has risen up the environmental, nutritional and political agenda. 

There weren’t many soil zoologists in my day – perhaps a handful in the country. Now I bet there are even fewer. A few months ago, RASE were raising concerns about the Dwindling Science base, as it poses a threat to soil health[9]. And even they didn’t mention soil zoologists. It is quite an indictment on how we value our soils that there are so few.

Instead of loosing carbon from the soil, we should be considering soil sequestration[10]. Perhaps if Agriculture were included in the Cap & Trade Emissions Scheme, twe may be able to make some money to pay for more research. It is far safer to consider ways to increase the amount of carbon in the soil, than pipe vast amounts of carbon dioxide (??pressurised to levels that present a hazard) all the way across the country into the North Sea. (and wait for it to explode? Check out)

Imagine Growing Weeds to save the World..

Hon Research Fellow, Centre for Food Policy, City University


[1] http://www.unep.org/Documents.Multilingual/Default.asp?DocumentID=97&ArticleID=1503

[2] http://sitem.herts.ac.uk/aeru/indicators/explorer/resource_d26.htm

[3] http://www.defra.gov.uk/environment/quality/land/soil/documents/evidence-paper.pdf

[4] P.Bellamy et al, Nature, Vol 437, 8.9.2005.[4]

[5] http://www.defra.gov.uk/environment/quality/land/soil/documents/evidence-paper.pdf

[6] http://www3.interscience.wiley.com/journal/117991504/abstract

[7] http://www.co2science.org/articles/V8/N38/B2.php
Charlie Clutterbuck,
Oct 11, 2016, 6:33 AM