What if lightning never struck?

Flash! Lightning lights up a stormy sky. Then comes the rumble of thunder.

What if lightning never happened? Would we miss it?

Lightning is one of nature's most dazzling sights: a giant spark that lights up a storm cloud. The National Weather Service says lightning strikes the United States about 25 million times a year.

It can be dangerous, so the safety rule is simple: when thunder roars, go indoors. But lightning also does some surprising jobs in nature. So what would happen if it never struck at all? This thought experiment follows three ideas: plant food, forests and thunder.

Lightning is an electrical discharge that temporarily equalizes charge regions in a thunderstorm. About 25 million flashes reach the United States each year (NWS), and most flashes overall stay inside clouds.

This thought experiment asks which natural processes depend on lightning. Facts come from NOAA, the National Park Service and Nature Education; consequences are reasoned ideas. The safety message stays the same throughout: when thunder roars, go indoors.

Inside a storm cloud, tiny bits of ice bump together. They build up electricity.

When there is enough, zap! Lightning jumps to balance it out.

Inside a thunderstorm, bits of ice and small hail bump past each other as air carries them up and down. The bumping separates electric charges: the bottom of the cloud usually becomes negative and the top positive.

Air doesn't let electricity flow easily, so a huge amount of charge builds up first. When there's enough, the air gives way and lightning flashes. NOAA says most lightning, about 75 to 80 percent, never leaves the cloud. Only some flashes reach the ground.

NOAA notes that exactly how lightning forms is still debated, but leading theories involve charge separation by collisions between ice, graupel and supercooled droplets, producing a negative cloud base and positive top. Air is a good insulator, so the field must grow strong before breakdown.

Because the field inside the storm is much stronger than that between cloud and ground, roughly 75–80 percent of lightning occurs within the cloud. The discharge heats its channel to as much as 30,000 °C (54,000 °F).

In our pretend world, storm clouds still bring rain.

But there are no flashes and no thunder. What else would change?

In our pretend world, storms still form and rain still falls, but the charge in clouds never jumps as lightning. No flashes, no strikes, no thunder.

Follow the paths in the lab: food for plants from the air, forests that renew after fire, and a quiet sky with no thunder. Some of lightning's jobs might be done in other ways, and some might change a lot. Each card says whether it's a fact or an idea.

Assume thunderstorms still develop and precipitate, but breakdown never occurs. That removes lightning's nitrogen fixation, lightning-ignited fires and thunder at once.

The interesting question is substitution: nitrogen is mostly fixed by microbes, and fire can have other causes, so the consequences differ in size. These are reasoned ideas; the premise itself is not physically realistic.

Air is full of nitrogen. Plants need nitrogen, but they can't use it straight from the air.

Lightning's huge energy changes a little of it into a kind plants can use.

Nitrogen makes up nearly 80 percent of the air, and every living thing needs it. But plants can't use nitrogen gas as it is. It first has to be changed into another form, which is called nitrogen fixation. The two nitrogen atoms in the gas are held together very tightly, so breaking them apart takes a lot of energy.

Lightning has that energy, so it fixes some nitrogen. But most nitrogen fixation is done by tiny living things called bacteria, including bacteria that live in bumps on the roots of plants like peas and clover.

N₂ is very stable because of its triple bond, so converting it into biologically available forms, nitrogen fixation, needs a great deal of energy. Nature Education explains that most fixation is carried out by prokaryotes, some free-living and some symbiotic, such as Rhizobium in legume root nodules, while some nitrogen is fixed abiotically by lightning or by industrial processes including fossil-fuel combustion.

So lightning is one supplier among several. Without it, microbial fixation would continue, though some ecosystems might receive less fixed nitrogen from the air.

Some forests grow back after a fire. Some pine cones only open in the heat!

Park rangers know that fire can help those forests make room for new trees.

The U.S. National Park Service explains that fire is an important natural part of many forests. In Grand Teton National Park, lodgepole pines have cones that open with the heat of a fire, dropping seeds onto freshly cleared ground. Aspen and other plants there are boosted by fire too, and wildlife from elk to grizzly bears benefits from the fresh growth.

Today, park fire managers use carefully planned fires and some lightning-started fires to keep forests healthy. This careful work is done by trained fire crews.

NPS Grand Teton describes fire as an important natural disturbance. Each ecosystem has a fire regime: ponderosa pine forests have frequent, low-intensity fires, while Greater Yellowstone's lodgepole and mixed conifer forests burn every 100–300 years in large fires. Lodgepole serotinous cones open with heat, seeding the cleared ground.

Fire was feared and suppressed for much of the 20th century; today managers use prescribed and lightning-ignited fires to restore natural fire regimes, while reducing fuels around communities.