Trees and the TMEX

Just before the recent federal election in Canada, the Liberal party committed to planting two billion trees over the next 10 years, the cost of which is to be “offset by forthcoming revenues from the Trans Mountain pipeline.”  However, a closer look at the proposed deal shows that sequestration of carbon dioxide by two billion trees will never compensate for the additional emissions generated by the expansion of the TMEX pipeline.

According to the Liberal Party pamphlet, over a ten-year period, planting a total of 2 billion trees is estimated to absorb and store about 30 million tons of carbon dioxide. How does that compare to the emissions caused by the new pipeline?

The TMEX, when operational, is intended to increase the capacity of the existing Trans Mountain pipeline by 590,000 barrels a day. Production in the tar sand region will ramp up to meet this newly available capacity.  That’s the whole point of building a pipeline.  Mining and refining bitumen from the tar sands deposits produces large emissions of greenhouse gases.  According to the Oil Climate Index, emissions from the tar sands are estimated to be as high as 174 kg of equivalent carbon dioxide per barrel of crude      

Doing the math, we can calculate that ramping up production by 590,000 barrels a day will generate an additional 37.5 million tons of greenhouse gases a year. So over a ten year period, the TMEX pipeline will generate emissions of about 375 million tons of CO2 equivalent (MtCO2e). During the same period the 2 billion trees will sequester less than one tenth of the carbon in these emissions.  To put the additional pipeline emissions in context, 37.5 MtCO2e a year is greater than the combined emissions of the cities of Calgary and Toronto, which in 2016 were respectively 18.2 and 18.3 MtCO2e/year. So operationalising the TMEX pipeline is like adding two major Canadian cities to the landscape.

Planting two billion trees is a great idea. It’s just that they can’t compensate for the additional greenhouse gas emissions from the Alberta tar sands generated by the TMEX pipeline. Canada should definitely plant lots of trees. But how many?

A trillion trees ?

A report this year published by the Institute of Integrative Biology in Zurich found that the restoration of forests is one of the most effective strategies for resolving the global climate crisis.  The institute  calculated that one trillion trees could potentially sequester and store over 200 billion tons of carbon—which would make a significant contribution to drawing down atmospheric levels of carbon dioxide, the principal greenhouse gas.

On a per capita basis, and spreading the tree planting program over 30 years from 2020 to 2050, we can calculate that Canada’s contribution to this ambitious global effort should be to plant about 160 million trees a year—about the same order of magnitude on an annual basis as the Liberal party’s proposal—although for a longer period: thirty years instead of ten. Two countries have already shown that this is a feasible proposal.  In Ethiopia this year, the government organised the planting of 350 million trees in 12 hours! That beat the earlier record set by India of 250 million trees planted in 2016.

But there’s a serious problem. Canada’s forests are under attack from insects and wildfires. The result is that net carbon emissions from all areas of managed forests are positive, not negative.  In other words, Canada’s forests are a net source of carbon, not a sink. The graph on the right is from a Canadian government report and clearly shows that net emissions of greenhouse gases have been increasing. Why then plant more trees?  Won’t this result in even more greenhouse gases being pumped into the atmosphere?

The thin line shows net emissions of greenhouse gases. It swings positive after about 2001, meaning that Canada’s forests are a net source of GHGs, not a sink.

If trees are planted in areas of natural forest, they are vulnerable to wildfires and infestations by insects. These two disturbances are the reason why Canada’s forests are a now a net source of  greenhouse gas emissions.  But what if these additional trees were being managed by towns and cities across Canada? Urban forestry should substantially reduce the risk of fire, and the trees could be more closely supervised and protected against insects.  

City trees bring substantial benefits to urban dwellers. They filter and clean the air of dust and fumes and reduce levels of ground-level ozone. They release moisture into the atmosphere cooling the air and creating a microclimate that reduces temperatures in the summer months. They reduce traffic noise.  And they make city streets way more attractive.

Toronto’s Trees

For example, let’s take a look at Toronto. The Greater Toronto Area (GTA)  has over 34 million trees.  The tree canopy cover  has been measured at 26 % which is a respectable number.  However, Torontonians want more trees, and the city has committed to raising its canopy cover to 40%. How many more trees does this represent?  A bit of simple math shows that this would mean that an additional 18 million trees need to be planted across the GTA.  Since the land area of the GTA is about 712,500 hectares, these additional trees on average are going to be planted at roughly 25 trees per hectare.

The 40 percent solution

Just as a thought exercise, let’s suppose that every town and city across Canada pledged to match Toronto’s initiatives and decided to up their game. Each municipality is going to commit to matching Toronto’s ambitious program and ramp up their tree canopy cover from its present value, which is likely around 20%, up to a target of 40%, effectively doubling the number of trees in urban areas across Canada. The area of urban municipalities in Canada is more than 27.5 million hectares, and a bit of math leads us to an estimate of almost exactly 1 billion trees. This is the number of trees which would need to be planted by urban municipalities across Canada in order to reach a 40 percent tree canopy cover over these towns and cities, assuming their present level of cover is about half that amount.

So here’s the plan.  It’s not necessary to organise for the next 30 years. Let’s just start with what we can do right now.  We set a target for 2025.  We work towards that, and then see where we are, and what we need to adjust as we work towards 2050. The most important action is to get started. Every town and city in Canada signs up to the 40 percent pledge and calculates how many trees it needs to plant between now and say 2025 in order to meet that target.

This plan gets Canada part way towards meeting its contribution to the one trillion trees objective—which for Canada adds up to 4.84 billion new trees by 2050.  But it’s a significant start. Most importantly, it’s driven by municipal action.  Many people feel paralysed by the frightening stories about climate tipping points and impending doom. But action taken by municipalities is enormously important, and this is where ordinary citizens, organised into active and determined community groups, can have a huge influence.  

The Liberal government promised Canadians two billion trees. So the other one billion trees should be planted by the forest services on land where wildfires are infrequent and insect infestations hopefully manageable.  Perhaps in Atlantic Canada?  But for the proposed federal government deal where we get lots of trees if they can build their pipeline?  The answer is thanks, but no thanks. We’ll take the trees; you can keep the TMEX.


There is a lot more information about the climate crisis and how to solve it in my new book. You can check it out here : //

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