Freaked out about the future of the planet? Don't let fear ruin your finances

"Do ETFs, REITs and mutual funds still make sense to invest in if the planet won't survive 'til our retirement?"

So read an Instagram DM from a friend earlier this year. The reasoning was fairly clear: A recent report from the United Nations indicates that climate change is harming the world's food supply to a catastrophic degree, while a 2018 U.N. panel found that humans have 12 years to significantly reduce carbon emissions to ensure a "safe and sustainable" planet. The Amazon rainforest — AKA the lungs of the planet — is currently on fire, which could speed up climate change.

It might seem hyperbolic, but the Insta-messenger is far from the only member of Generation Y worried about the health of the planet to the extent that it affects their outlook on the future. Almost 90% of millennials recognize that man-made climate change is happening, leading some to experience what the American Psychological Association refers to as "eco-anxiety."

"Gradual, long-term changes in climate can also surface a number of different emotions, including fear, anger, feelings of powerlessness, or exhaustion," the APA noted in a 2017 study on the mental health effects of climate change.

With the planet at stake, who can blame you for not saving 10% of your income for a future you're not sure will arrive?

While it's easy to feel powerless, Daniel Swain, a climate scientist at the National Center for Atmospheric Research and the Nature Conservancy at UCLA, tells CNBC Make It that he has a more positive outlook on the state of things than what is typically portrayed in the media.

Climate change will have significant impact in our lifetime, he says, but it's also manageable if we do something about it now.

"One of my goals these days has been to really push back against the notion that the world is ending," says Swain. "Increasingly, I think there is this ennui, or this feeling that there's not a lot that individuals can do to stop the problem. But the challenge is that it's individuals in aggregate who potentially can solve the problem."

At just 30 years old, Swain is squarely within the demographic that seems to be losing hope. Indeed, he says weather events will become increasingly extreme, and humans will have to adapt to new ways of living. But he wants to make it very clear that now is the time to take action that will have "tremendous impact" on the Earth for "centuries and millennia to come." Especially in wealthier countries, like the United States, which have historically emitted the largest amounts of greenhouse gases.

In fact, he says if anything, he and his fellow climate scientists are more energized than ever. Now is exactly the time to invest more, not less: In the future we want, in policies we believe in. And that definitely includes saving up for a sizable emergency fund.

"If I thought I was going to get sick in the future, I would want to make damn sure I have good insurance, I wouldn't throw my hands up," he says. "It motivates me, personally, to want to leave as much of a cushion for the future as possible. If you're worried about the future, in every other context, you'd want as much of a buffer as possible."

Not saving because you don't see the point is only hurting yourself. Emergency fund aside, though, Swain acknowledges that many of the "investments" he's talking about have little to do with personal finance. He says increasing reliance on renewable energy, rethinking transportation systems and making eco-friendly policies easy to adapt and access across the socio-economic spectrum will have the biggest impacts, and save everyone money down the line.

Amy Zalman, CEO and founder of Prescient, a foresight consultancy, echoes Swain's cautious optimism, telling CNBC Make It while it's well-known that humans tend to focus on all of the "bad things that will happen," it's wiser to prepare for both positive and negative outcomes.

"Prepare for all possibilities," Zalman says, noting financial experts always advise people to save for a rainy day. "What if you also think, Well, maybe I should save for a sunny day."

Like Swain, she says it's time to expand the notion of what it means, exactly, to invest.

"If you do have actual money to invest, put it in places, small and large, where people are really thinking about how to make the earth sustainable," she suggests, like startups that are rethinking agricultural practices.

While it can be easy to be consumed by pessimistic thinking — especially given the daily headlines — humans need to think about the world they want to live in, and act to make reality reflect it, Zalman says.

"Just being optimistic is not enough," she says. "It's important to have a story about the future of the world that I want to live in that helps me."

Swain stresses that what humans are dealing with right now is not an "apocalyptic situation." Millions will be affected, and they will need money to move, rebuild or deal with other climate change-related disasters. But it's not the end of civilization. The Earth will still be here; systems will still be in place.

"The challenge is some people probably won't see nearly that much loss, while others are probably going to lose everything," he says.

For the record, Swain has a "modest" amount of retirement investments in "fossil fuel divested funds," part of a category of socially-responsible funds that have grown in popularity for the past three years, according to Morningstar, as investors take the threat of climate change more seriously.

Socially-responsible, or "impact," investing is built on the premise that where you invest your money matters. If you want the world to be a "better" place — socially, environmentally, religiously or however you define it — than you should invest in companies that operate under those same ideals. You can invest in "ESG" or "SRI" funds through all of the major brokerages. Different funds focus on different things: Some promote environmental stewardship, while others invest in companies promoting women and minority rights.

Just know that this type of active investing can come with higher fees than passive investments and uncertain gains, as can all investing. There is also an ongoing, existential debate over whether any company can actually do good, and whether or not investors would be better off investing in traditional index funds and ETFs and donating their returns to organizations that align with their values.

Swain acknowledges that one person investing in those funds is not stopping climate change in its tracks, but he says "it sends a signal," and it's a concrete step any individual investor can take.

"Among my personal friends and family, I don't know anyone who is not investing because they don't think the future is worth investing in," he says. "I am optimistic about the future, so I need to save a lot more."

Don't miss: How to slash your eco-footprint—and save money at the same time

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