Alan Stahler: Diversity equals survival
Imagine you’re a critter, growing up in a world where nearly every other critter … wants to eat you. A shell covers your body. The harder the shell, the more likely you’ll survive.
No matter how much you wish your shell were harder, there’s nothing you can do about it – you’re stuck with the shell you were born with. Some of your neighbors – by luck of the draw – have inherited genes for harder shells, making them better-protected.
With all those hungry mouths about, those of us with harder shells are more likely to survive … and to pass those hard-shell genes on to future generations. By selecting – choosing – which individuals survive, the hungry mouths are exerting selection pressure on the population, pushing it to evolve harder shells.
Critters with hungry mouths, however, are not blind to what their dinner is doing … their mouths, too, are evolving. Those with harder teeth … or teeth that work like saws, or drills … will eat more. They, too, feel selection pressure: Over the years, predators evolve a better bite.
The evolution of two species – each responding to the other – is co-evolution. But co-evolution need not involve species working against each other. Species can co-evolve through co-operation. The close cooperation among flowers and bees evolved out of millions of years of such cooperation.
Plants are good at pulling water out of the soil … not so good at pulling nutrients out of the tiny particles of rock in the soil.
Fungi, on the other hand, are good at pulling nutrients from rock. They attack the rock chemically, break it down, pull out minerals and atoms. But, unlike plants, fungi cannot make their own food.
Like living cobwebs, fungi grow around and into the roots of plants, feeding minerals and atoms to the plants.
Harnessing the energy of sunlight, plants use those nutrients to make food … and not just to feed themselves. Through their roots, plants send the fungi a healthy slice of the food they produce.
Fungi feed plants … plants feed fungi … plants feed us.
If only it were that simple.
We’re in the kitchen, cooking up a meal … only to find that a key ingredient is missing. A quick dash to the grocery should solve that problem. But, to get that ingredient onto the grocery shelf, it had to be trucked over from a warehouse … before that, processed in a factory … grown on a farm (shipped through the Suez Canal?) … all sorts of steps, to get it into our meal.
You and I are newcomers to this planet. By “you and I”, I’m addressing, not just my readers … but all humans … all members of the animal kingdom … and the plant kingdom … and the fungal kingdom …
Life evolved on Earth close to four billion years ago. For the first two billion-or-so years, there were no animals, plants, or fungi … life consisted entirely of two groups of organisms, both single-celled: Bacteria and archaea (“are-KEY-uh” … which look just like bacteria, but live very differently. Some archaea, for instance, live in hot springs, in water way too hot for bacteria to survive.).
When – after roughly two billion years – animals and plants and fungi evolved, the bacteria and archaea welcomed us … as new places to live. Right from the start, they moved in, and continue to live, in our gut, on our skin … and in the soil. Much of what “we” do to keep ourselves alive – much of the chemistry, the trading of atoms – is done for us, by our microbiome. Sterile mice, kept bacteria-free in the lab, quickly die.
So it is in the soil. Attempts to simplify the soil ecosystem – say, by growing just one crop over vast acreages – risk the same fate as sterile lab mice.
There is a lesson in the history of life: Diversity builds resilience. As summed-up by Charlie Brown: “I need all the friends I can get.”
Al Stahler enjoys sharing science and nature with friends and neighbors in The Union and on KVMR-FM. He teaches classes for both kids and grown-ups, and can be reached at email@example.com.
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