FOOD FOR THOUGHT (Part II) – Like sands of the hourglass, so are the days of our soils (with apologies to Socrates). By Rob Blakemore Feb., 2017
Q.- Apart from species extinctions, what is most pressing global environmental health/security issue (and most ignored)?
A. – Unglamorous topsoil loss at an irreplaceable rate of 2,000 tonnes per second.
Q. – How so?
A. – Because soil provides 99.7% of food (plus all our fibre/timber and it filters all drinking water). Soil is foundation of all primary production and thus supports biodiversity too.
Q. – Says who?
Q. – Oops! Can it be fixed?
A. – Yes, but only if we urgently redirect all our efforts & resources into education & recycling organic ‘wastes’ in order to do what Lady Eve Balfour (1947) advocated:- “Feed Earthworms”.
Despite best efforts of our humus-worm workforce, here’s some background info….
Nett topsoil loss by erosion (water, wind, tillage) is estimated by FAO (2015) at 25-40 billion tonnes per year with median 32,500,000,000 t per yr (or about -33 Gt / yr topsoil loss). A year has 31,536,000 seconds. Thus about 1,000 tonnes / sec topsoil is lost.
Surprisingly, total Global topsoil resource is unknown; an estimate is 4,000 Gt (Ref.). If so, we have (4,000 Gt / 33 Gt/yr) = ~121 years of topsoil left.
That’s not too urgent. But… FAO calculate just 60 years more of harvests and, as only 10% of land is arable with rates of erosion & degradation 100-1,000 times higher (FAO 2015: 103), without renewal it is possible our farms have just (121 / 10% =) 12.1 years!
And Pimental & Burgess (2013: 447) have even more worrying data estimating fertile soil lost from agricultural systems worldwide is 75 Gt / yr; more than twice the FAO rate given above, = 2,000 t tonnes / sec topsoil loss thus even 12 years may be optimistic. This is why rivers are brown and the air dusty around farmland.
Such a timescale may seem extreme although, if my reasoning is correct, arable topsoil loss is the most urgent problem and has the most ramifications. Now that is food-for-thought… As a rapid solution, the broad conversion to organic farming/permaculture as a priority may yet “Feed Us All” says Worldwatch Institute (2006) whilst also, incidentally, preserving biodiversity, sequestering carbon and saving both water & fossil energy.
Indeed, as Darwin (1837, 1881: 169) told us, we need to re-appreciate the humble, heroic earthworm who he said creates ~14.09 t/acre/yr castings = 35.4 t/ha/yr x 1.5 Gha arable land = +53 Gt/yr rebuilt topsoil. However, a major discrepancy is that FAO (2015: 103) now estimate just 0.15 t/ha/yr topsoil formation; if on 9.5 Gha of non-ice/desert land = 1.4 Gt/yr globally. Possibly, industrial/chemical farming since the 1940s has depleted worm populations by 50-80%, or more. So the only hope for ‘Survival of the Species’ is to reverse erosion & extinction by aiming to double earthworm humus production.
The following graphic summarizes the issue. [Note that food follows irrigation up to recent times and that excess chemical poisons are now used while earthworms decline].
Unsustainable agrichemicals, food & Humanity vs. Earthwormity (as proxy for topsoil loss); just as the ‘Green Revolution’ depleted topsoil, a ‘Brown Revolution’ is needed to recreate it.
Conserving earthworms (vermicomposters & field worms) is the best & only way to rebuild topsoil/humus as is simply & graphically demonstrated in the following photo.
Here’s the article’s earlier pdf version if you need hard copy – FOOD-FOR-THOUGHT-II.