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— AM

This week:

Sucking it up: Tree-planting as carbon-reduction strategy

Climate strikes can be found in every corner of the world

Your suggestions for living sustainably

Are trees the silver bullet for capturing carbon?

(Fred Tanneau/Getty Images)

As promised in last week's newsletter , we're taking a look this week at tree-planting as a strategy for sucking carbon out of the atmosphere.

Both Australia and New Zealand aim to grow one billion new trees over the next decade. Pakistan launched its so-called Billion Tree Tsunami in 2014. After restoring 350,000 hectares of forest ahead of schedule, Prime Minister Imran Khan launched a 10 Billion Tree Tsunami in 2018 with a five-year goal.

But does planting trees always reduce carbon in the atmosphere?

Scientists argue that, done right, tree-planting works as part of the wider effort to reduce carbon. One advantage? It can be done relatively easily and quickly on a large scale, said Julia Pongratz, a climatologist and earth systems modeller at the University of Munich. "It's working, right? We've been planting forest for 10,000 years."

Pongratz said forestation could remove 500 to 7,000 megatonnes of carbon from the atmosphere a year. Some studies put the figures even higher.

But we should be careful about assuming that trees alone can save us. A recent CBC article debunked the idea (popular on Facebook) that Canada's abundant trees can sequester any carbon we produce. The truth is that our trees may actually emit more carbon than they absorb, as a result of wildfires and natural die-off.

And not all tree-planting operations are the same. Commercial operations tend to favour fast-growing ones planted in grid formation. The aim is quick turnover — trees that are ready to harvest in 40 to 60 years.

Malcolm North, a research scientist with the U.S. Forest Service, said newer, commercially grown forests only sequester and store carbon temporarily. "The wood that goes into making paper or more transient wood products … only sequesters carbon for a few years, and then it's back in the landfill decomposing, [sending] that carbon back into the atmosphere."

Governments may be more likely to try to reforest land that was previously razed by fire or cleared for crops or cattle grazing.

North said the ideal scenario is maintaining the forests that are already there. Cutting down old-growth forest and replacing it with more commercially viable trees can be detrimental.

That's because you're implanting something that isn't in sync with the ecology of that particular location. North said scientists worry those new forests "may not be very resistant to global warming, may not be resistant to the disturbance regimes, like fire, that are endemic to that system."

Over a 10,000-year period, most of these tree-planting strategies are probably moot, North said, "because the trees eventually die one way or another, and that carbon does go back in the atmosphere."

North said the next 100 to 150 years are "really crucial" in transitioning to a low-carbon economy, and "forests are an effective tool for a period of time like that to be able to reduce the amount of carbon that's in the atmosphere."

That's why countries like Pakistan and its 10 billion trees will make a difference.

If tree-planting is "done in a way that's not one size fits all, and they're trying to restore a more natural forest system," North said, "then I think it's one of the best things we can do."

— Stephanie Hogan

Your environmental goals

We always welcome feedback.

Email us at whatonearth@cbc.ca.

Old issues of What on Earth? are right here .

The Big Picture: Worldwide climate strikes

Skolstrejk för klimatet. What began as a series of solitary weekly school boycotts by a Swedish teen named Greta Thunberg has become a global movement. On May 24, students in 110 countries marched in the latest iteration of the Fridays for Future climate protests — even in war-ravaged Syria (see tweet below). This particular group of activists lives in Rojava , a city in northern Syria, and wants to increase renewable energy and reforest a local nature reserve. Last week, Thunberg, who was recently profiled in Time magazine and has been nominated for the Nobel Peace Prize, called for another global strike on Sept. 20. But this time around, she is issuing a further challenge: "Adults, will you join our youth?"

(GreenRojava/Twitter)

Hot and bothered: Provocative ideas from around the web

More on trees: The Philippines has just passed a law that stipulates high school and college students have to plant 10 trees in order to graduate . If everyone sticks to this pledge, it could result in 175 million new trees every year.

Decarbonizing air travel will not be easy, but one B.C. seaplane company seems undaunted. Harbour Airlines, which makes 30,000 short-haul flights every year between places such as Vancouver, Victoria and Seattle, has partnered with a Washington company that developed an electric-propulsion system. The aim: to become the world's first all-electric airline .

Increased use of public transit is seen as a key part of any move to a low-carbon future, and Mont Tremblant, Que., (population 10,000) is doing its part. As of June 21, it will be free to ride transit there . One of the leaders in this realm is Tallinn, Estonia, which started offering free transit in 2013.

It isn't easy being green — but you're trying

(Steven Senne/Associated Press)

To celebrate the warmer weather, we asked readers to share some of the steps they've taken to reduce their carbon footprint and live more sustainably in general. Here are a few of your responses.

Diane Boisjoli wrote to say: "We are reducing our use of plastics by using biodegradable compost bags in all our garbage cans in the house. We also avoid using plastic vegetable bags at the grocery store. We are going to the Bulk Barn with our own glass and metal containers. We are walking more to do neighbourhood tasks. We are hoping to get a hybrid car in the next year. We already heat with electricity, being in Quebec makes this easy."

Sébastien Picard tallied a few of his household's sustainability measures, which include cycling, "no long-distance travel," "less meat," "[opening] windows first before using AC" and convincing "our 19-year-old to not buy a car."

Paul Mitchell provided this list: "1. Plant a vegetable garden to supply my household with fresh produce instead of going to the supermarket. 2. Supplement our fruit and vegetables needs by utilizing the local farmers' stall around the corner. 3. Replace the 20-year-old furnace and air conditioner with new energy-efficient models. 4. Reduce the travel miles for vacation time. 5. Hand dig out the weeds from the lawn instead of using herbicide."

While many people are changing their habits now, David Tilsworth sent an email that itemized how far back his sustainability efforts go.

"Well, 35 years ago I bought 10 acres and planted 3,500 trees," he said. "The house used geothermal heating, which is 5X more efficient than gas. Twelve years ago, I bought a new house with R60 [a grade of insulation] in the ceiling and R30 in the walls. My heating and cooling costs are 30 per cent [that] of our neighbours. We installed only gardens and trees, no grass to mow."

The 10-kilowatt solar panel array on his roof generates about 11,000 kilowatt hours a year, "which is enough to power five efficient homes like mine." He drives an electric car (a Chevy Volt), which "has carried us 57,600 kms over the past three years on electricity which we generated." (He noted that "the remaining 70,000 kms was unfortunately using gas.")

And, as a kicker, he wrote, "we stopped using plastic, one-time shopping bags about 20 years ago."

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Editor: Andre Mayer | Logo design: Sködt McNalty