Is it physically possible to plant 100 million trees per year?

Labour’s eye-catching promise to plant two billion trees by 2040 is not particularly believable. 

All the major political parties have pledged to plant millions of trees as part of a larger ‘green’ strategy. The Conservatives have committed to 30 million trees a year until 2024, while the Liberal Democrats want 60 million a year until 2045. Labour’s plans add up to 100 million a year. While this all sounds like a valiant cause and one that may be applauded by some, this forestry arms race raises more problems than it solves. 

Let’s start with the logistics: planting two billion trees by 2040 amounts to 270,000 trees per day or 190 trees per minute, 24 hours a day for 20 years. This is certainly a large number, and it gets even more difficult when you realize that you cannot plant year round. The planting season is more like four or, at a stretch, six months. In the best case scenario of a six month planting season they would have to plant 500,000 trees per day.  

The infrastructure required for this project is phenomenal. Will the trees be planted by hand, which is incredibly labour intensive, or by mechanical means, which brings extra costs and potentially negative environmental impacts? 

Either way, it would require a large temporary workforce for this specific purpose. This raises questions such as what will these workers do in the non-planting months? Where are they coming from? UK unemployment stands at just 3.8%. It is unlikely many of those will be capable and willing to do the job.

Where will the seedlings come from? The state of North Carolina produces 15 million seedlings in their nurseries each year. North Carolina, which is approximately half the size of the UK, is a very heavily forested state and depends on its forestry output as a large portion of the economy. Their infrastructure has been built up over the years for specifically this purpose. Does anyone believe they could increase their production between six and seven times overnight? 

In order to grow 100 million seedlings per year you will need approximately 3,300 acres of greenhouses/nurseries. Assuming there is enough supply and infrastructure to get the 100 million seedlings each year (even more when you consider the mortality rate), where are they going to be planted? Assuming a planting density of 500 trees per acre, you’ll need over 300 square miles each year or 6,250 square miles in the next 20 years. This is equivalent to almost 7% of the UK landmass. 

And now for the science: a critical factor to look at are the species of trees, the plan for the forests, and the long-term environmental impacts. 

Planting 190 trees a minute for 20 years gets us to two billion more trees, but only if all of the trees survive. This is unlikely. The normal two-year survival rate of trees is 80%. This reduces the actual number of new trees, only to be further reduced as more trees die before reaching maturity and peak growing years. 

They will also need to consider what type of trees are going to be grown and planted. Evergreens such as pine, spruce and firs are easier to grow and plant but a more diversified forest that includes hardwoods such as oaks and maples would be better for wildlife, national parks, and the overall health of the forests. A homogeneous forest is much more susceptible to disease, insects and other environmental dangers. 

Let’s also hope there are no forest fires in these areas for the next 20 years: every forest fire is — in a sense — a double penalty on the CO2 emission scale.The fire kills the trees and stops them from absorbing future CO2 while at the same time releasing the stored up CO2 in the trees as they are burned.

So given all those considerations, will planting billions of trees help the UK become carbon neutral? Two billion trees will take care of 47 million tonnes of CO2 per year but this is a gross number. There will be emissions involved in getting the trees to their stage in life when they can actually “clean” CO2 from the atmosphere. And don’t forget the amount of CO2 that will be put into the atmosphere from building and maintaining nurseries, heating and cooling the greenhouses, fertilizing the seedlings, transporting them to the planting sites and planting itself — especially if using mechanical means which may be required in order to physically plant this volume of trees.

If something sounds too good to be true it usually is — this is especially so when a politician says it, doubly so during an election.

Richard Schondelmeier has a Bachelor of Science in Forestry and a Masters of Science in Forest Resource Management from the University of New Hampshire