Bruce M. Beehler is a naturalist and author of 12 books, including “Birds of Maryland, Delaware, and the District of Columbia” and “North on the Wing.”

It is late October, and I just closed my back door to shut out the fast-flying Asian tiger mosquitoes that have become a persistent nuisance in D.C., where I live. A warming world has allowed this invasive species to expand across the United States and extend its foraging season deep into autumn. Asian tiger mosquitoes weren’t even in Washington 25 years ago. My mosquito problem won’t be on the agenda at the United Nations’ COP26 climate change conference, which begins Sunday in Glasgow. But it is an example of the myriad ways — sometimes minor and annoying, sometimes terrifying and deadly — that climate change is not only a global threat but also an intensely personal and local one.

In conversations with my colleagues about this issue, we all say the same thing: “How can smart people doubt climate change? It is happening right outside our back door!”

A D.C. neighbor reminded me that warmer nighttime summer temperatures and higher humidity have meant our tomato plants now produce less fruit and suffer from fungal disease. And our backyard gardens no longer host the common bumblebee. We have recently read in The Post about how local farmers are being forced to adapt to changing climate conditions to avoid crop losses. Even our backyards’ poison ivy is getting stronger and itchier.

More substantive climate consequences, affecting people’s yards, homes, businesses and health, are apparent across the country.

Consider this week’s headlines: A nor’easter is drenching New England, while California recovers from what The Post called “a Level 5 out of 5 atmospheric river” that dumped inches of rain and created mudslide conditions in areas previously wrecked by climate-change-driven wildfires.

They’re part of a larger story of sea-level rise, storm surge, coastal flooding, cratering sinkholes and intense rain events (all climate-driven) that have led to more home losses. The increasing severity of supercell storm events (which can include tornadoes) across the country has taken a toll on our housing as well as our power grid. Already in 2021, there have been 18 weather/climate disasters, each producing more than $1 billion in damages.

A recent article in the Lancet noted that climate change is fast becoming the defining narrative of human health. Allergies and asthma are on the rise because of a changing climate. Unfamiliar tick-borne diseases proliferate as their vectors move ever northward. It used to be just Lyme disease. But now add to that ehrlichiosis, babesiosis, anaplasmosis, Rocky Mountain spotted fever and the alpha-gal syndrome — all transmitted by ticks that are on the march.

And ever-more-common extreme heat events are a regular killer. The heat wave that hit the Pacific Northwest in late June killed at least 100 people in Washington state.

Climate change is harming local businesses, too. Economically important salmon runs in the Pacific Northwest are failing because the loss of alpine snowpack leads to the drying-out of Pacific-flowing streams and rivers. Along the Atlantic coast, the lobster fishery retreats ever northward as sea temperatures rise. In Alaska, a melting underground glacier has closed part of the only access road in Denali National Park, shutting down a whole host of tourism businesses. Ski areas in the Northeast continue to suffer from winter warming, reduced snowfall and the inability to manufacture snow when temperatures rise above freezing.

In New York’s Adirondack Mountains, lumber harvesters have fewer cold winter days when they can access timber — the roads (formerly frozen) bog down and the lake ice does not hold the trucks that must cross to get to the cut logs. In Canada, outdoor ice hockey is in massive decline. And across New England, the snowmobile season suffers mightily because of warming and melting snow. The same goes for cross-country skiing. All of these cost businesses in small towns their profits, and people their jobs.

The arid West is in the grip of a multi-decadal drought that has emptied reservoirs and reduced stream flows that serve as the lifeblood of farms, rural towns and coastal cities. Perhaps the Western forest fires serve as the most compelling example to contemplate, because they have endangered lives and livelihoods. The interaction of drought, fire and local weather has created a troubled environment where a suburban home can go up in smoke overnight. Ancient sequoias are killed, neighborhoods are lost, air becomes unbreathable, and businesses incinerate. Thirty-nine million acres of forest burned in the United States (mainly in the West) in the past five years. That’s an area almost half again the size of the state of Virginia.

The effects of climate change are already in your backyard, and mine. The only major uncertainty is whether the world’s leaders can muster the political will to do something meaningful about it in Glasgow.