STORRS, Conn. — One of the difficulties in trying to figure out how much we should be worrying about climate change is that the effects are a little hard to understand. They either seem so far in the future or they seem like such small changes. The average temperature is going to rise a couple of degrees by the end of the century: Is that such a big deal?

One recent study has identified one change that’s occurring in Maine. In itself, it may not be a big deal, but it is one example of the kinds of change that are likely occurring all around us already and which will continue far into the future.

That study looked at the plants in the alpine area atop Bigelow Mountain in western Maine. We recorded all of the plants there and recorded how abundant each was. Then we compared what’s there now with what was there 33 years ago, when an earlier survey was done.

We found that the trees occur in places now where they didn’t occur before. And although shrubs aren’t occurring in new places, they are more abundant in the places where they do occur: They’re bigger. At least one of the herbaceous plants in the alpine community is less widespread than it used to be.

These changes are similar to what is being found in alpine communities on mountains all over the world, and in the Arctic as well. Shrubs, especially, are becoming more abundant, and trees are starting to move upslope into areas where they couldn’t survive before.

Are these changes occurring on other mountains with alpine plants in Maine and New Hampshire? Probably, but we can’t say for sure because no one did surveys on other mountains 30 years ago, so it’s hard to quantify any changes that may have occurred since then.

It’s important to say that we don’t know precisely what’s causing the changes in the alpine plants on Bigelow.

The temperature is warmer now, certainly. Winter temperatures in Farmington are 2 degrees higher, on average, than they were a century ago. For alpine plants, that translates into a longer growing season.

But the temperature is not the only thing that’s changing. We know that nitrogen, which falls from the atmosphere, has increased dramatically in the past several decades. We put it in the atmosphere by driving our cars and burning fossil fuels to heat our homes.

Plants are very sensitive to nitrogen. Nitrogen is a fertilizer, but it helps some plants and hurts others.

So we can’t say exactly what’s caused the alpine community on Bigelow to change. We know it’s something we did (and are still doing), but we’ve changed the environment in so many ways that it’s hard to know which change is affecting the plants.

What would be the consequences if the shrubs and trees continue to become more dominant in the alpine communities?

It’s likely that we’d lose a lot of the low alpine plants — plants that grow only out in the open and can’t survive under the trees and shrubs. These are exactly the plants that define alpine plant communities, so, in effect, we’d lose our alpine habitat in the Northeast. Our mountaintops might eventually all be covered by trees, as most of them are already.

Big deal? Not really.

Those of us who like to hike the mountains of the Northeast and appreciate the different plants that occur there – plants that we’d otherwise have to go to Labrador or Greenland to see – we’ll notice the change.

The great views we have now from these mountaintops would be lost.

The list of plants that occur in the region would be diminished by the loss of the specialized plants that occur in alpine areas and can’t live elsewhere.

But life would go on. Alpine plants have been through this before as the environment has changed over millions and millions of years. They may not occur in Maine, but they’re likely to survive farther to the north.

Although alpine plants have been through dramatic climate changes like this before, we have not. We are creating an environment unlike anything that humans have experienced, at least since we stopped being hunter-gatherers and settled down roughly 10,000 years ago.

Declines in alpine plants are just one kind of change. But they are one of many, and that is what’s important. We may not know yet exactly what those changes will be, but they’re coming. We can count on that. Some are occurring already. And those many little changes will transform the world into a place that could be quite unlike anything we have ever seen before.

Robert S. Capers is a plant ecologist at the University of Connecticut. He studies alpine plant communities.

— Special to The Press Herald