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A rising tide sinks all boats… eventually

A rising tide sinks all boats… eventually

Have you heard that ice cream causes murder or that global warming has led to an increase in piracy? Apparently in Maine, consuming more margarine leads to more divorces, while increased US spending on science, space and technology results in increases in suicides by hanging, strangulation and suffocation.  Actually, these are examples of spurious or false correlations – entirely unrelated things whose data appear to suggest a causal relationship.  And in these examples, the outcome is little more damaging than a few humorous media articles and a couple of books.

False correlations, however, run deep.  And some can have a pernicious impact on large numbers of us.  Consider for example, the well-worn neoliberal saying that “a rising tide raises all boats.”  It is based on two mistaken premises.  First, that employment is always a route from poverty to prosperity; and second, that an increase in overall employment must benefit everyone.  And it is for these reasons that continued economic growth is the altar upon which all else must be sacrificed.

The evidence for the benefits of economic growth for all is far more nuanced.  In pre-industrial economies where most people worked the land, there is little evidence that much growth occurred beyond that allowed by the ups and downs of the annual harvest.  Indeed, it took the economies of the British Isles until the eighteenth century to re-reach the technological level of the Roman Empire; so what economic growth their had been amounted to a catching up following a major economic collapse.  And even during that period of lethargic growth, various plagues and famines – including the catastrophic Black Death in the fourteenth century – rapidly threw economies into reverse.

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Garden Logic – understanding correlation and causation in our gardens and landscapes

Garden Logic – understanding correlation and causation in our gardens and landscapes

This home landscape is managed using science-based methods; the only routine additions are water and arborist chip mulches.

Upon reading this post’s title, you may be inclined to stop right there. (That’s why I have an eye-catching photo to lure you in.) While logic may seem irrelevant to your enjoyment of gardening, I can guarantee that reading this blog post will challenge many seemingly logical assumptions you’ve heard or read about. Recognizing unsubstantiated assumptions and avoiding their pitfalls means you can make wise choices about how you care for your gardens and landscapes.

You can find this and thousands of other silly correlations at www.tylervigen.com

A few definitions are needed before we get started:

Correlation refers to variables whose changes mirror one another. For instance, the addition of nitrogen fertilizer to container plants is correlated to plant growth: as nitrogen levels increase so does plant growth. You can also have inverse correlation, where the variables move in opposite directions. An example is water availability in soil and planting density: the more plants you have in a specified area, the less water is in the soil.

Plant growth is correlated with increased nitrogen and other nutrients (from Xu et al. 2020)

Causation takes correlation one step further: it establishes that one of those variables is causing the change in the other. Using the same examples, we know through published evidence that the increase in nitrogen is causing the increase in plant growth, and the increase in planting density is causing the decrease in soil water because of competing roots. These relationships are obvious to us, but what’s important is that these causative effects have been established through scientific experiments.

Inverse relationship between planting density and soil water content (from Shao et al. 2018)          

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Olduvai IV: Courage
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Olduvai II: Exodus
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