Earth Day, which is a week from Monday, serves as a reminder to all of us to redouble our efforts at minimizing our impacts on this globe and do what we can to help the millions of species with which we share this Earth.

Climate change represents one of the most dramatic changes our world is experiencing. The timing of various biological and meteorological events attests to our altered climate. Ice-out on our lakes is earlier now, as is the first appearance of leaves on many of our trees, the first flowers of many plants, the first singing of spring peepers, and the spring-time arrival of migratory breeding birds.

We are also seeing the northward expansion of the ranges of many mobile species. Turkey vultures, red-bellied woodpeckers, tufted titmice and Carolina wrens are all well established in Maine now but were rarities 40 years ago.

Climate change, habitat fragmentation and pollution collectively challenge the survival and successful reproduction of many birds. Birdlife International finds that 1,469 of the roughly 10,000 bird species are in danger of extinction. That’s one of every seven species.

Partners in Flight estimates that songbird abundance in North America has declined by more than a billion birds since 1970.

Based on the first-year results of Maine Breeding Bird Atlas, compared with the first atlas (1978-83), it seems clear that nesting of bank swallows, cliff swallows and tree swallows has fallen precipitously. All catch insects on the wing. Entomologists are concerned about declining insect populations. Fewer insects may lead to fewer insect-eating birds.

Frankly, we have done a poor job of looking out for nature in the Lower 48 species. But there is a large and important habitat in North America that is still largely intact, the North American Boreal Forest. This biome stretches from Alaska to Newfoundland, occupying 1.5 billion acres. The NABF has experienced no industrial development, and human populations are limited.

Within this biome, one can find extensive bogs and fens, large lakes and rivers, and Alpine habitats as patches in the thick coniferous forest. Wildlife biologists estimate between one and three billion birds nest in the NABF each year. It’s no wonder some have bestowed the title of “North America’s bird nursery” on the NABF.

Although Maine and other northern states have pockets of boreal forest, Alaska is the only state in the contiguous NABF. Most of the forest is Canadian.

More than 300 species of birds nest in the NABF, representing nearly 50 families. The forest is particularly important for 151 species that have at least a quarter of their breeding population there; 35 of those species have at least 80 percent of their breeding population in the NABF. That latter group includes the solitary sandpiper, boreal chickadee, palm warbler and Lincoln’s sparrow.

Many birds in the NABF move south for the winter. Some, like surf scoters and dark-eyed juncos, may go no farther south than Maine, while others, like blackpoll warblers, winter in South America.

Because migratory birds connect different areas, bird conservation requires attention to all portions of the range of a species. For the NABF, the Boreal Songbird Initiative is playing a leadership role in conservation of this area.

The chief scientist on the Boreal Songbird Initiative is Dr. Jeff Wells. He grew up in Bangor, went to college at Maine-Farmington and earned his doctorate at Cornell, working at the Cornell Lab of Ornithology. These days he’s based in Hallowell.

To conserve the present diversity of the NABF, no more than 50 percent can be lost to forestry and other uses by indigenous people. That seems attainable.

Climate change is the more serious threat. Reducing carbon emissions everywhere will help, as will targeting and conserving so-called climate refuges in the NABF that likely will offer relatively cool habitats in the future as the climate continues to warm. Check out the Boreal Song Initiative website for more details of this important conservation effort.

Herb Wilson teaches ornithology and other biology courses at Colby College. He welcomes reader comments and questions at whwilson@colby.edu.