It was the old-growth forest in Great Smoky Mountains National Park that helped me understand how very unnatural my hometown nature really was.

I grew up in a heavily wooded area in the Hudson Valley of New York, where my childhood rambles through the woods would often include hopping over hand-built stone walls. The walls were there because my forest haven had, a couple hundred years earlier, been farmland. The Dutch and English settlers had utilized the area's prolific rocks, turning a frustration into a building material.

It wasn't until my late 20s, on that hiking trip into the Smokies, that I saw what old-growth forest on the East Coast looked like. While the trees in the never-logged or never-farmed areas of the park aren't quite as large as the redwoods of California or the untouched areas of the Olympic Peninsula, they're big, and the ecosystem is notably different from the woods I'd grown up in, thanks to the influence of these giants. The Smokies visit showed me how my woods at home likely looked before Europeans came to New York in the 1600s and began changing the landscape.

A dirt road winding through the woods in Garrison, NY. The historic dirt roads that run through my hometown of Garrison, New York, are hundreds of years old, but the extensive forest belies the fact that the whole area was once farmland altered by human hands. (Photo: Starre Vartan)

Everything that I grew up with was second- or third-growth forest. It made me wonder then, was the landscape I grew up in even really "natural"? It's a question that's being asked more often as the human population continues to expand into formerly wild areas while others simultaneously look to protect natural spaces. But first, don't we have to define what nature is?

What is wilderness?

I'm not the only one asking such questions. The geologic era that we are living in (technically the Holocene) has been so profoundly influenced by human activity that some scientists are suggesting we name a new era after ourselves — the Anthropocene (see the video below). While some scientists argue it's "pop science" to suggest that humans are causing changes akin to geologic forces, others say it's appropriate: Human changes to the Earth at multiple levels are that profound.

It's not just climate change. "The atomic era, for instance, has left traces of radiation in soils around the globe, while deeper down in the rock strata, agriculture’s signature in Europe can be detected as far back as A.D. 900," reports Joseph Stromburg in Smithsonian.

And while modern humans have been responsible for a number of extinctions (the passenger pigeon and the dodo being the most commonly known), prehistoric people may have helped kill off species too, along with other significant ecosystem-wide influences. According to a paper in the Proceedings of the National Academy of Sciences (PNAS), "... by the Late Pleistocene, humans had begun to engage in activities that have led to alterations in the distributions of a vast array of species across most, if not all, taxonomic groups. Changes to biodiversity have included extinctions, extirpations, and shifts in species composition, diversity, and community structure."

We have been changing the Earth as long as we have walked upon it.

A question of conservation

If we've been killing off animals and changing the composition of the Earth with nuclear weapons, altering climate and changing the landscape with agriculture, hasn't most of the Earth — in one way or another — been fundamentally altered by humans?

That question matters because the answer has implications for what we mean when we work to conserve natural spaces. What does "conserve" mean, if ecosystems have already been changed by human preferences over time? And what does "natural" mean? For many of us, the idea is to return, say, a given piece of land to its "original" state, before humans came along and logged or quarried or farmed it. But it's hard to know what that state was, given the impact humans have had over such a long time.

Dr. Nicole Boivin, the University of Oxford archaeologist who led the research published in PNAS, told the Daily Mail, "If we want to improve our understanding of how we manage our environment and conserve species today, maybe we have to shift our perspective, by thinking more about how we safeguard clean air and fresh water for future generations and rather less about returning planet Earth to its original condition."

This idea that we work from the place we currently find ourselves, rather than looking at an unknown past to determine a future course, isn't an excuse to give up on setting aside lands away from too much human influence, as it is a reframing of what is natural.

Humans are natural, too

Or are we a natural force ourselves? Another way of thinking about the whole question of what's "natural" is to consider that human beings are a part of nature, too. Therefore most of what we do is part of the natural process. This can be hard to wrap your head around if you've seen the top of a mountain cut off for coal removal, or a just-logged forest, or a denim-dye polluted river choked with dead fish.

But certainly, not everything we do is destructive, and some of it is neutral. For instance, how is a human-built stone wall different from a bird's nest? Fundamentally, it's not. At the same time, the scope of human impact on the Earth, the degree to which we displace other animals from their homes, and how far we take the transformation of materials — from crude oil to plastic, for example — is much more significant and most importantly, problematic for other species, compared to what other life on Earth does. Taking that concept further, the argument could be made that plants have also changed the Earth significantly over time, but their growth and proliferation almost always expanded where and how other life on Earth can survive, whereas much of what humans do has the opposite effect.

The idea that people are nature is intriguing, because it requires a rethink about our ideas of conservation. Along the lines that Boivin points out, we'd have to look more at the future of life on Earth and less at the past — since we can't really know what a pre-human Earth was really like.

Most likely we will land somewhere in between. There are some places where trees have continued to grow (almost) untouched for thousands of years, and most of us would agree those spaces should be off-limits to human tampering. But there are many places where our impact has been tremendous and continuing (America's great cities), or significant but then more gentle over time. I would argue that my hometown is one of those latter places — and indeed, much of the Northeast, which is more forested than it was 100 years ago. What of these "new" human-influenced natural spaces? Do they deserve protection too? If so, what kind?

When conservation is destructive

I've been watching this confusing debate play out where I'm currently living in Berkeley, California. Here and throughout the Bay Area, 100-year-old eucalyptus trees, planted by people at the turn of last century, are being cut down because they're not native. Local saplings and bushes are being planted in their stead. Entire forests of trees are being ripped down, all at once, which hardly seems akin to nature's (generally) more gradual timelines. And what of the animals and insects that have been living in the eucalyptus?

Planting native species is still forcing a human idea of what's "supposed to be" in a place. When the trees don't plant themselves through nonhuman processes (wind, animals moving seeds, etc.), how natural are they, really?

The idea behind this chopping down of trees is that by planting natives, the "original" Bay Area nature will be returned once the trees establish themselves. Of course, that land is still fractured by highways, roads and the car culture that continues unchecked here, the continuous building on ever-steeper slopes in defiance of the earthquake faults that lie below, and the lack of top predators that have been extirpated along with most of the wildlife that would be living where people now do. Oh, and all this in complete ignorance of the fact that climate change will be changing up the types of flora and fauna that will be able to live here as this part of the country becomes more like the desert south of it. The Bay Area's "natural" areas may be wonderful, but they are laughable as some kind of example of what "should" be here. Yet that's the justification for the native-planting project.

When cutting down trees en masse and replacing them with other trees that may have called this place home in the past — which is now inhabited by a 100,000 people (and seemingly just as many gas-belching cars) and the entire climate of which will be changing in the next 100 years is called "conservation of nature" — well, the time seems ripe for a redefinition of what those words even mean.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.