Larkspur: IELTS Academic Reading practice test

Soil is not dirt, and the difference is not sentimental. A handful of good agricultural soil is a mixture of mineral particles ground from rock, decayed organic matter, water, air, and an enormous population of living organisms, of which a single teaspoon may contain more individuals than there are people on the planet. It is also made extremely slowly. Estimates vary with climate and parent rock, but the formation of a centimetre of topsoil is generally reckoned in centuries rather than decades, which means that on any timescale a farmer or a government can act upon, soil is not a renewable resource at all.

What makes soil work is less its ingredients than its architecture. The particles are bound into crumbs, and the crumbs into larger aggregates, by the threads of fungi growing through them and by glues that microorganisms secrete as they feed. Between the crumbs are spaces, and those spaces are the point: they let water soak in instead of running off, they let air reach the roots, and they give a root somewhere to go. Break the aggregates and the same mineral particles behave like a different substance entirely, shedding water from the surface and setting hard as they dry.

The southern Great Plains of the United States had been grassland for as long as anybody could establish. The grasses there put a large share of their growth below ground, into root systems reaching several metres down, and those roots held the soil through droughts that arrived every couple of decades. From about 1914 the land was broken up on an extraordinary scale. Wheat prices were high, the disc plough and then the tractor made it possible for one family to turn far more ground than before, and a succession of wet years persuaded everybody that the rains were normal. By 1930 many millions of acres of grassland had been converted to wheat.

The drought began in 1931 and lasted, on and off, for most of the decade. With the wheat dead and the grass gone, there was nothing holding the surface, and the wind lifted it. Dust storms rolled across the plains carrying soil thousands of feet into the air; on one afternoon in April 1935, remembered afterwards as Black Sunday, a front of dust advanced across several states and turned day into darkness. Dust from the plains fell on Washington and on ships several hundred kilometres out in the Atlantic. Over the decade some two and a half million people left the region, and the federal government created an agency specifically to deal with soil, which it had never previously thought necessary.

The remedies that followed are now textbook practice: ploughing along the contour rather than up and down the slope, planting rows of trees as shelterbelts to break the wind, alternating strips of crop with strips of grass, and leaving the stubble of the previous crop on the surface instead of turning it in. What is less often noticed is the shape of the original mistake. Every individual decision to plough had been reasonable. The price was good, the machinery was available, the neighbours were doing it, and a farmer who declined would simply have earned less while the wind removed his soil anyway. The disaster was produced by rational people acting sensibly within a system that priced none of the consequences.

Erosion did not stop in 1940; it stopped being visible. Soil continues to move off cropland by wind and water, and most published estimates suggest that on a large fraction of the world's arable land it is leaving faster than it is being formed. Those estimates should be treated with some care. Measuring erosion is genuinely difficult, the figures depend heavily on the method used, and the most alarming numbers in circulation come from models rather than from measurement. The uncertainty runs in both directions, however, and a wide error bar around a bad number is not a reason for comfort.

The practices attracting most attention now aim to keep the soil covered and living roots in the ground for as much of the year as possible: sowing directly into the residue of the previous crop without ploughing, and growing a cover crop between the cash crops rather than leaving the field bare. Both reduce erosion substantially, and both have been promoted with claims about yields and about storing carbon that run some way ahead of the evidence. It is also worth saying plainly that not ploughing usually means controlling weeds by other means, and in practice that has often meant more herbicide, not less.

The deeper difficulty is that soil depletes on a schedule nobody notices. A farm losing a millimetre a year looks exactly the same at the end of a career as it did at the beginning, and the yield can be held up for decades by fertiliser that replaces the chemistry while doing nothing for the structure. Almost every institution we have for managing resources is built to respond to visible change. Soil offers none, until a dry decade arrives and removes in five years what was taken five thousand to make.

Creativity has become a curriculum subject and an industry. It appears in national education frameworks alongside literacy and numeracy, it is the stated purpose of a large market in corporate workshops, and it is regularly named in employer surveys as the capacity most wanted and least often found. Behind all of this sits an assumption that is rarely stated and even more rarely examined: that creativity is a general ability, possessed in some degree by everybody, and capable of being increased by exercises that are not about anything in particular.

Testing the assumption requires a measure, and the measures are the first difficulty. The standard instruments are tests of divergent thinking, which ask a person to produce as many uses as they can for a brick or a paper clip and score the answers for number, variety and unusualness. They are quick and they are reliable, in the narrow sense that the same person scores similarly on two occasions. Their relationship to creative achievement in the world is weaker: correlations with later accomplishment are real but modest, and above a certain level they disappear altogether. Scores also rise with practice at taking the test, which is exactly what one would not want from a measure of a general capacity.

With that caveat in place, the training literature is more encouraging than sceptics expect. Several meta-analyses of creativity training programmes report moderate positive effects, and, more usefully, they agree about which programmes work. The effective ones teach specific cognitive procedures: how to state a problem in several different ways before attempting to solve it, how to search deliberately for an analogy in an unrelated field, how to defer judgement while options are still being generated. The ineffective ones are the ones that exhort. Programmes built around encouraging participants to be imaginative, to take risks or to think differently produce very little. There is a catch, and it is serious: the outcome measured is almost always a divergent thinking test, and the training frequently teaches, in effect, how to do well on it.

A second body of evidence points in a different direction. Creative achievement is overwhelmingly specific to a domain. People who produce original work in organic chemistry are not, as a group, unusually original in choreography, and the correlation between creative output in unrelated fields is close to zero at the level that matters. Nor does achievement arrive early. Across music, mathematics, painting and the sciences, major contributions almost always follow a long apprenticeship in the field, typically of a decade or more, during which the individual acquires not only technique but a sense of which problems are worth attempting. Whatever creativity is, it appears to be something that happens to people who know a great deal.

These two findings are usually presented as being in tension, and the tension is supposed to be resolved by the concept of functional fixedness: the more expert a person becomes, the more their knowledge constrains what they can imagine, so that the outsider sees the possibility the specialist cannot. Laboratory work does show the effect is real. People who know what a box of drawing pins is for take longer to see that the box itself can be a shelf. But it is hard to find much support for the stronger version, in which important advances come from outside a field. What the historical record shows more often is that they come from the edge of a field: from people who entered it late, or who moved into it from a neighbouring one, and who therefore possess the knowledge without having absorbed all of the habits.

Elena Barros, who studies curriculum design, argues that the whole enterprise rests on a category error. Creativity, in her account, is the name of an outcome and not of a faculty. We call a solution creative after we have judged it useful and surprising, which is a verdict on the product rather than a description of a process inside the person; and a school that timetables the outcome is reasoning as it would if it set aside two hours a week for being right. Her practical objection follows from this. Hours given to content-free creativity lessons come out of the subject teaching that supplies the knowledge on which any actual creative work depends, and the trade is being made without anyone noticing that it is a trade.

She is half right, and the half she is wrong about matters. If creativity were a content-free skill, it should transfer between domains, and it plainly does not. But something does transfer, and the training literature identifies it fairly precisely: not a capacity but a set of procedures. Generating options before evaluating them, reformulating a problem statement several times, hunting deliberately for the structural analogy in another field, tolerating an unfinished state for longer than is comfortable. These are modest, they are learnable, and every one of them does its work on material the learner already knows. They are not an alternative to expertise. They are a way of getting more out of it.

The question worth asking, then, is not whether creativity can be taught but which part of a creative performance is general. The evidence suggests the answer is the procedures rather than the power, and that has a straightforward implication for how schools should proceed. A creativity lesson detached from any subject teaches procedures with nothing to apply them to, which is why such lessons are so often remembered as enjoyable and so rarely as useful. The same procedures taught inside the history lesson, on a historical problem, by somebody who knows history, have something to bite on. Creativity, if it belongs on a timetable at all, belongs there as a way of teaching subjects rather than as a subject of its own.