In recent years, large-scale tree plantation programmes have exploded in popularity
as a way to tackle the climate crisis.
Today we will be planting 20 million trees.
Who's against the trees? I mean, the trees ... Everyone's for the trees.
And it's easy to understand why.
These trees, they store masses of carbon dioxide from the atmosphere.
They give us oxygen we breathe, they are really the most amazing ecosystems.
And there's no disputing that the right trees in the right place is a good thing.
However, this type of large-scale tree planting is becoming a problem.
Because, while anyone can plant a tree, it doesn't necessarily mean we should.
This is Yatir forest, this is Israel's largest planted woodland.
It was once held a green triumph, holding back the desert, storing much-needed moisture,
and reducing CO2.
But the four million trees are actually having an overall warming effect on the planet.
This is because of something called The Albedo effect,
which means the ability of a surface to reflect heat based on its colour.
The bright desert surface that was there before reflected more sunlight than the current darker tree canopy
that replaced it.
That's right, this forest is making global heating worse.
What the Yatir forest highlights is that choosing the right location is crucial.
Planting in the wrong type of soil, near too many grazing animals,
or in the wrong climate, are all factors that will kill off new saplings very quickly.
The wrong location can also deplete groundwater, dry up streams and kill off peatland,
like this one, approved by the UK Forestry Commission,
which in addition to destroying the important ecosystem, also releases the huge carbon deposits stored within it.
Choosing the right location isn't the only challenge for large-scale tree plantations.
Most of the time, these tree planting programmes choose monocultures.
Consisting of only one species, monocultures store less carbon, are terrible for biodiversity,
and are also highly susceptible to disease.
It is ecosystems, not just trees, that capture and store carbon.
And diverse ecosystems secure the most carbon most securely.
Another big problem is planting the wrong type of tree.
In South Africa, the introduction of non-native varieties of acacia has led to this highly invasive tree taking over
vast areas of land, including precious heat lands and grasslands.
The country now spends millions of pounds clearing the trees every year.
Similarly, in the UK, the non-native Sitka spruce has decreased biodiversity
by creating barren forest floors due to its dense treetop canopy.
Large-scale tree plantations often target land that communities depend on.
About 12 farms have been sold recently in mid-Wales to companies who plan to offset carbon emissions
and invest in timber.
Across the world, approximately 300 million people work or live on land
targeted by large-scale tree plantation programmes.
And perversely, there are instances where communities have been incentivised
to cut down the old forest, because planting new trees pays more.
For instance, farmers in Costa Rica are given $125 a year for each hectare of plantation they establish,
but only $39 a year, if that land is used to protect natural regeneration.
There's a strong argument to say that large-scale tree plantations aren't an efficient or effective solution
to restore the trillions of trees lost over the centuries, nor fix the climate crisis.
We actually lose about 10 billion trees every year through wildfires, deforestation and other means.
So, protecting the forests we already have would be a better use of our time and resources.
Forests are actually really good at restoring and expanding themselves,
so we should allow space around established forests for them to naturally expand.
This is called natural forest regeneration and it's by far the best way to get more trees on the planet.
One place where planting trees is good is in urban areas.
Trees help reduce noise, improve air quality, help prevent flooding, provide shade,
and even improve your physical and mental wellbeing.
So yes, the right trees in the right place are vital.
But the fact remains that there is no one solution to the climate crisis.
We have to use all the tools at our disposal to reduce greenhouse gases and slow global heating.
We're losing forests at a terrifying rate, much faster than we can plant or restore them.
But the forests are growing back,
and if you want to see where they're growing back, I'll put a link in the description to a project that is tracking
forest regeneration all over the globe.
And if you want to learn more about this topic, my colleagues Phoebe Weston and Patrick Greenfield
did a great two part special on the Guardian science weekly podcast
as part of their Age of Extinction series.
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