I have been coping with a major dose of what I will call "the layman's dilemma" - who do I believe? In the last few months a number of reports have collided on my desk. They say different things about the same general topic – soil health, soil productivity and land degradation.
The entree to the issue is by way of a letter from the president of the International Union of Soil Scientists (dated August 1, 2017) to fellow soil scientists expressing concern about soil health. He asserts that man's activities have "…… aggravated the extent and severity of soil degradation in all biomes, but especially in soils of managed ecosystems". The last phrase is a flash way of saying soils used for agriculture.
This letter is dwarfed by a huge report emanating from the United Nations Convention to Combat Desertification called Global Land Outlook. It proclaims that the current system of food production is broken and that a "significant proportion of managed and natural ecosystems are degrading". More specifically, it is claimed, "Over the last two decades approximately 20 per cent of the Earth's vegetated surface shows a persistent declining trend in productivity mainly as a result of land/water use and management practices."
Compare these industrial-strength pronouncements of doom and gloom with the following.
An international group of scientists has used satellite technology over a considerable length of time (1982-2009) to measure the state of the Earth's vegetation. They measured what they called the Leaf Area Index (LAI).
In their words, they found "…… a persistent and widespread increase of growing season integrated LIA over 25 per cent to 50 per cent of the global vegetated area."
In other words, the Earth is becoming greener. And even more astounding, they could attribute this greening (at least 70 per cent of the effect) to the increasing concentration of carbon dioxide in the atmosphere. Remember, carbon is one of the 16 essential plant nutrients and plants breath in carbon as carbon dioxide from the atmosphere. From the plants' perspective carbon dioxide is a fertiliser.
The results of this study would appear to contradict the messages emanating from an international leader in soil science and from the UN. This situation frequently arises in science – at first glance the available evidence appears contradictory.
What to do? One path through such dilemmas is to ask: Is there other independent evidence to bring to bear on the issue?
In 2011 Max Roser of Cambridge University started a website called Our World in Data. It is just that – a repository of data about our world. It is fascinating. Scroll through graphics in the section Yields and Land Use in Agriculture. It really does not matter which combination of crop and country you choose, the message is the same. Crop yields per unit area are increasing across the globe.
How can this be if soil health and productivity is declining? Perhaps any loss in production due to declining soil health is offset by the incremental improvements in plant genetics and crop husbandry together with increases in the use of fertiliser and pesticides? More evidence would be helpful.
I have a cousin, Dr Greg Edmeades, who is also an agricultural scientist, but unlike me he spent much of his science career working in overseas science organisations, primarily focused on improving crop yields in third world countries. He and some colleagues recently addressed the question: Will we be able feed a world of 9 billion people by 2050?
They reviewed long-term trends in the yields of wheat, rice, maize and soybeans across a number of countries including third world countries. The data shows that the annual increase in the yields of these crops was about 1-2 per cent, due largely to improvements in plant genetics. They also found that there were large gaps between the yields achieved commercially and those recorded in controlled, well managed, research trials.
They concluded: "We remain cautiously optimistic that the world will be able to feed itself in 2050, based on the existence of large and exploitable yield gaps, especially in sub-Saharan Africa and South Asia, and the steady gains made by plant breeders…" No mention here of declining soil health and productivity.
So where does this leave us? We have two compilations of international data indicating that the productivity of soils is improving versus an opinion piece from a leading soil scientist, one would hope based on some data, and a large gloomy report from the UN. Can these different conclusions be reconciled?
I decided to go back to the UN report and dig a little deeper. At page 55 there is a strong hint.
"It must be clearly understood and communicated that 'land productivity' in the context of the Land Productivity Dynamics (LPD) dataset strictly refers to the overall above-ground vegetation biomass productivity. This is not conceptually the same as, nor necessarily directly related to, agricultural income per area unit or 'land productivity' as used in conventional agricultural terminology."
In other words they have applied a different meaning to the word "productivity". In their definition soil productivity includes all the so-called "ecosystem services" that the land offers and not just food production per unit area.
And at this point my bias goes on display. "Ecosystem services" and its related concept of "natural capital value"' are recent attempts to introduce ecology into soil science.
There are many like me who see this as a dangerous development. It is dangerous because it allows agricultural science to be captured for political purposes. Indeed our first attempt at this marriage has been a disaster, for these concepts are the foundation upon which the Horizons One Plan is currently floundering.
When seen in this light the whole UN report reduces to a diatribe about how mankind is destroying the planet - hence their conclusion, "the current system of food production is broken".