Should we be planting trees?

[Fishnut]

Ahead of the last general election all the main parties pledged to plant a load of trees. iNews said that the Conservatives pledged 30 million trees/year until 2024, Labour pledged 2 billion trees by 2040 and the LibDems pledged 60 million/year until 2045. That's a lot of trees. Unsurprisingly, though, even the fairly modest target of the Conservatives has yet to be met.

I have some issues with tree planting. They seem primarily (at least at a government level) to be seen as a carbon capture solution, yet my understanding is that the number of trees needed to effectively counter the amount of carbon we're emitting is far greater than is practical. It's also not clear to me (though admittedly it's not something that I've looked into that much) that this is a proper carbon capture solution rather than a temporary stay of execution - trees, after all, die and rot and their carbon gets released back into the environment. They seem to be 'theatre' rather than a solution - a big and obvious thing that makes it look like we are acting when really we're not doing that much at all.

Other issues I have are that I've seen little discussion about the types of trees or where they are being planted. Locally, I've seen them being put in recreational spaces with seemingly little thought to what happens if/when they get bigger. It just seems to be 'this is council land so we can stick x number here' with little consultation with those who use those spaces and no aftercare. And we've discussed in other threads (that I cba to search for right now) how large-scale tree-planting schemes have damaged or destroyed valuable habitats such as bogs and grasslands.

I'm happy (even eager) to have my concerns assuaged. I'm also not against trees and recognise that our country was much more wooded than it is currently and there's value to restoring those woodlands. My main question is - should trees be the focus of our climate/biodiversity commitments? Should we be spending millions growing and planting them? If we should, are there any studies/recommendations/reports that discuss how best to plant trees to produce the greatest positive impacts?

[Grumble]

The other side of this is that tree planting is less efficient at increasing the number of trees than simply leaving areas alone, especially next to existing woods.

[Bird on a Fire]

There's been a few papers recently showing that plantations don't store anything like as much carbon as previously thought - below-ground carbon was such a big black box that we've been massively underestimating the importance of soil carbon. Planting trees on a temperate grassland, for instance, can even be carbon positive.

Natural regeneration is much for effective for carbon sequestration, at least unless we can figure out how to accelerate development of a carbon-storing microbiome. It's also way better for biodiversity, if course.

I'd argue that the case for planting trees is pretty much limited to regions (particularly those in the tropics) where deforestation has caused such huge changes (eg soil erosion, loss of seed dispersing animals and pollinators, etc) that regeneration can't occur on a practical timescale. And even then, you can achieve a lot by planting "islands" of naturalistic veg and letting nature do the rest.

Huge amounts of the public debate have been hijacked by forestry industries and their political representatives.

[Bird on a Fire]

They seem primarily (at least at a government level) to be seen as a carbon capture solution, yet my understanding is that the number of trees needed to effectively counter the amount of carbon we're emitting is far greater than is practical. It's also not clear to me (though admittedly it's not something that I've looked into that much) that this is a proper carbon capture solution rather than a temporary stay of execution - trees, after all, die and rot and their carbon gets released back into the environment.

Purely on this front - the main bulk of carbon storage in temperate forests is below ground. When trees die and rot most of the organic matter becomes soil, and takes a very long time to be re-emitted to the atmosphere (though heating, droughts and fires all accelerate it).

A conservative estimate puts the carbon storage potential of reforestation at about 75 GT, which is a couple of years of global emissions. It would be a non-trivial help, but there's no way round leaving most fossil fuels in the ground. ETA link https://annforsci.biomedcentral.com/art ... 020-0922-z

"The right tree in the right place" is the slogan British conservationists have been pushing. It can be a very good thing, when done well, but sadly it rarely is for (short-term) economic reasons.

[monkey]

"The right tree in the right place" is the slogan British conservationists have been pushing. It can be a very good thing, when done well, but sadly it rarely is for (short-term) economic reasons.

I was just going to pipe in with "trees can help with flooding too", but I guess that's covered by the "The right tree in the right place" bit.

I like trees and the associated wildlife. I don't mind more of them, even if planting a whole bunch is not a solution to climate change.

[Woodchopper]

They seem primarily (at least at a government level) to be seen as a carbon capture solution, yet my understanding is that the number of trees needed to effectively counter the amount of carbon we're emitting is far greater than is practical. It's also not clear to me (though admittedly it's not something that I've looked into that much) that this is a proper carbon capture solution rather than a temporary stay of execution - trees, after all, die and rot and their carbon gets released back into the environment.

Purely on this front - the main bulk of carbon storage in temperate forests is below ground. When trees die and rot most of the organic matter becomes soil, and takes a very long time to be re-emitted to the atmosphere (though heating, droughts and fires all accelerate it).

A conservative estimate puts the carbon storage potential of reforestation at about 75 GT, which is a couple of years of global emissions. It would be a non-trivial help, but there's no way round leaving most fossil fuels in the ground. ETA link https://annforsci.biomedcentral.com/art ... 020-0922-z

"The right tree in the right place" is the slogan British conservationists have been pushing. It can be a very good thing, when done well, but sadly it rarely is for (short-term) economic reasons.

As well as this, trees naturally regenerate. So old trees that die are replaced with young ones. The forest lives on.

[lpm]

I was reading something about bracken the other day. Was interesting.

Areas of bracken - e.g. in the Lake District - are ghosts of former woods. Cut down all the trees a few centuries ago and bracken takes over.

But the soil underneath is perfect for trees to return once again, still containing a seedbank of woodland species. Bracken is a signal that it'll be the right tree in the right place. Plant trees and their shade will kill off the bracken in a few years and diversity will return, is the theory.

PDF: https://greenhousethinktank.org/static/ ... ant_v1.pdf

[headshot]

I was reading something about bracken the other day. Was interesting.

Areas of bracken - e.g. in the Lake District - are ghosts of former woods. Cut down all the trees a few centuries ago and bracken takes over.

But the soil underneath is perfect for trees to return once again, still containing a seedbank of woodland species. Bracken is a signal that it'll be the right tree in the right place. Plant trees and their shade will kill off the bracken in a few years and diversity will return, is the theory.

PDF: https://greenhousethinktank.org/static/ ... ant_v1.pdf

If the sheep don't eat the saplings first...

[IvanV]

Ahead of the last general election all the main parties pledged to plant a load of trees. iNews said that the Conservatives pledged 30 million trees/year until 2024, Labour pledged 2 billion trees by 2040 and the LibDems pledged 60 million/year until 2045. That's a lot of trees. Unsurprisingly, though, even the fairly modest target of the Conservatives has yet to be met.
trees to produce the greatest positive impacts?

Let's work out how many trees it is. There's 1,000,000 sq m in a sq km. Plantation tends to be about a tree every 2-3m. So that's somewhere between a tree every 4-9 sq m. So probably tree planting is around 100,000 - 250,000 per sq km.

So, 2 billion trees, to take the largest of those examples, is about 4,000 - 10,000 sq km. With UK having an area of 240,000 sq km, this is around 2% - 4% of our present land area. With 13% of UK currently wooded, that's a material increase on the present dismal level. But not going to have a transformative effect on the landscape. Especially when we remember a large contribution to that 13% is extensive non-native commercial forestry in places like Scotland, which has only about 1% of its land in native woodland for all its apparently extensive "woodland". When you look at the OS map of counties in central England like Warwickshire, Leicestershire, Northants, Cambs, etc, there's barely any woodland at all across vast swathes of the country.

I have some issues with tree planting. They seem primarily (at least at a government level) to be seen as a carbon capture solution, yet my understanding is that the number of trees needed to effectively counter the amount of carbon we're emitting is far greater than is practical. It's also not clear to me (though admittedly it's not something that I've looked into that much) that this is a proper carbon capture solution rather than a temporary stay of execution - trees, after all, die and rot and their carbon gets released back into the environment. They seem to be 'theatre' rather than a solution - a big and obvious thing that makes it look like we are acting when really we're not doing that much at all.

There was news recently of people turning up in Wales and trying to buy farms, to turn to trees. What they were proposing was non-native commercial forest. Which apparently gets you your carbon credits, under some arrangement, just as much as restoring the land to native woodland. The locals were up in arms about it. There's a general perception that there is too much of such forestry, and people didn't want more of it. In this country, often there isn't even much money in cutting it down once you have grown it. It's not very good wood, labour costs are high, and you don't get the economies of scale from large-scale forestry. So you ruin the landscape with some crap non-native forest, and there's no value or jobs in it.

So yes, we have to be very careful about "plant lots of trees". During the 90s when there was a depression in land in general, and farmland in particular, I felt that would have been a very good time for the government to buy up a lot of land to convert to natural landscapes. It would have had the advantage of making farmland scarcer, so keeping the price up and thus making farmers better off, and better able to invest. But you have to do a good job in landscape restoration, not just cover it in any old trees.

[tenchboy]

Most planting schemes do indeed appear to be just for show: millions of trees are boasted and photo opportunities created to show off just how green are our credentials, " yes we may be destroying everything in our path but its OK because we're planting millions of trees, two foot apart in this field". Even if nine of every ten of those trees were to be removed they would still be too close together to flourish; you'll have an enclosed canopy made up of spindly, sickly sticks supporting a few tufts of foliage on the top. These plantations are no different from the industrial conifer plantations of the fifties sixties and seventies when it comes to an impoverished field/herb layer and non-existent ground layer caused by the lack of light: to create anything remotely worthwhile in terms of allowing sufficient space to allow a tree to grow and spread and create a proper crown you'd probably have to remove another nine of every ten after that: in a woodland, the spaces in-between the trees are as, if not more, important than the trees themselves, they need that space and light throughout their lifetime, they won't suddenly grow new lowdown branches if they are haloed in later life: a stick with a leaf on top will only ever be just that, a stick with a leaf on top. And always having been supported by neighbouring trees they will only have developed a very minimal root system; I've not seen pictures of the current storm damage but after the 'Great' storm it was noticable that it was the interior of many plantations that was devastated: the trees on the edges, having been buffeted, and having to support themselves throughout their lives had grown a better root-plate and were thus able to better withstand the onslaught.

They used to plant/manage oak standards with hazel coppice with just ten trees to the acre that is twenty two yards (ie one chain, an acre being ten square chains) apart so that the oaks would develop a full crown without excluding the light from the under-wood. This allowed growth of a shrub/sub shrub layer - elder, dogwood, dog-rose, bramble, say, and a rich field layer (annuals and herbaceous) - or if ash or chestnut coppice then for three or four years following the cutting the woodland floor would be awash with adapted plants - bluebells, primroses foxglove, wood anenome, which would flourish and set seed and decline as the coppice regrew and as the bramble and under-story grew back during the same time a nesting-site was created for the summer visitors - nightingales, blackcaps, etc, a diversity that arose through use; until after seven eight nine years of growth - depending on the size of the wood required - it would be cut again and all the semi-dormant plants - just hanging on in the semi shade would burst forth again and the dormant seed bank would burst into new life and the cycle would start again. The whole point of this is that successful woodlands were managed; they used to be used and their value and importance reflected that use, they survived because they were a resource, a source of valuable wood and timber for everything that as made and needed by everyone for all everyday living: every wood had its separate use and it was this management through use that created the woodlands we now see around us. Except that now we are more likely to see the remnants of years of neglect: the need for the produce has passed and with it the need for their conservation.

A field that is planted with trees and neglected will never flourish, will never support any great diversity of other wildlife - the necessary diversity of habitat just won't be there to support it. A single oak, or beech - too late to think about ash or elm now, gone the way of the lime - will have more foliage than all the sickly 'witches brooms' crammed into the same area and thus - presumably - more carbon capture - but also because of the open nature of the sight a vastly superior suite of associated flora and fauna underneath and surrounding it.

You can plant a field full of trees but in a hundred years time you will still only have a field full of trees, you won't have a woodland: a woodland is about diversity: diversity of species and diversity of age from sapling to fallen and rotting. A planted field will have trees of the same age and the soil will be too rich in nutrients to support the traditional shade tolerant plants of the traditional woodland and too shady to support the non shade adapted plants that can grow on the nutrient rich soils. Woodland is woodland because of its being useless for anything else; poor soil with species abundant adapted to poor soil which was either left as woodland (rarely) or became woodland (secondary semi/natural woodland) due to the soil being too poor to yield any significant crops. And you can't recreate foot-deep leaf litter thick with beetles and invertebrates and orchid seeds popping up as if from nowhere when the opportunity finally presents itself. (This despite, on one of the (?)motorway 'conservation' schemes (ie publicity stunts) their doing just that: huge diggers transporting tons of woodland soil to a new site and dumping it, "It's OK, Look what we're doing here!" They didn't put the spaces back into the soil though did they? Wump! dropped compacted, the whole soil system destroyed in front of the cameras: the spaces inbetween the particles are greater than the particles, that's how a soil 'breathes'.

For every great planting scheme that trumpets its millions of trees: take two noughts off the number of trees advertised as planted; and then halve it; factor in the cost of management, or consider it a wasteland: it will be forgotten and fail, and become a prime site for housing, just like farmland that is no longer required now that we can import cheap food from all over europe: once gone, lost forever. You would be better off creating a need for the woodland to be managed; then management becomes not just desirable but necessary; but that would only come about if people got fed up with plastic and wanted to return to hand crafted wooden products,which just ent gonna happen; and no-one will ever recreate the need for hazel for hurdles-making again because no-one will ever be folding thousands of sheep in temporary enclosures all out across the downs again; nor is there going to be any great demand for bean sticks or anything else. So first find some reason beyond public relations and carbon absorption to create a woodland, create it and manage it over an extended period of time, not just as a one off exercise and walk away (there was a story that I didn't keep regarding a council 'enhancement', ?five, ?ten years later, having been forgotten, it was a mass of scrubby bramble, its purpose totally forgotten: the whole lot was flailed to the ground to tidy it all up. Only afterwards did someone come along and ask,"why did the counci fatten our community woodland?"); maybe create it is an extension to existing woodland; (re)create your woodland for that reason and then your management and carbon capture and associated diversity will follow. Much broad-leafed woodland was lost when it was cut down and replanted with conifers during what Oliver Rackham described as 'The Locust Years' if the Forestry Commission were now to crop those conifers and, instead of replanting with more conifers, to replant with broad-leafed woodlands, you would/might be replanting english woodland on a suitable english woodland site where it might stand a better chance of surviving.

Many of those conifer plantations of past ages are now beyond their useful life: all that great investment for the future has become a liability: the cost of cutting and removing the timber is greater than its value as timber, the parks and estates that were planted up with forestry grants have been sold off: the mansion house is now apartments, the farmhouses have been tardisized (as you walk in through the door you suddenly find yourself inside a westminter penthouse all gleaming white and shiny chrome), the barns all converted to studios and swimming pools and the home meadow a tennis court and car-park: what on earth do these people want with a conifer plantation now?: it is now left to decay. Woodland is a very long term strategy, whether as an investment or an amenity and there will never be a guarantee that it will still be needed or valued when, in eighty or a hundred years time, it reaches its planned maturity: the world will have changed too much. Without a use, woodland is useless; create a need for it and comes alive.

Roe deer and grey squirrels would now also be a major problem. Most people see them rarely and the damage they do, never. Because of the deer - imagine thousands of wild cattle roaming over market-gardens or arable farmland, out of control, eating everything before them - woodland recruitment is a problem: crouch down as you walk through and look to each side, you will see a browse line about three feet off the ground showing a complete lack of vegetation - most noticeably with regard to ivy around the base of trees. Grey squirrel damage seems to come in cycles: on my own little patch it was almost unknown and then in one year I could have shown a dozen beech trees that had had great patches of their bark completely removed, smaller ~6" trees all around at the base, larger ones from the base of the larger, lower branches where they leave the trunk: that was maybe ten or twelve years ago now, the smaller of those trees have now rotted out and died, the larger are still dying. A start has been made as far as grey squirrels are concerned (I think/I'm almost certain) as it now illegal to release a grey squirrel back into the wild, but a significant cull would have to happen before a difference could be made; and the same for roe deer too: but that will never happen, you will never create a market for venison, for most people the sight of a deer grazing in a field will be the highlight of their year: nothing will ever persuade them of the need for a cull to protect the newly planted woodlands: so add miles of deer fence to the cost. (As an aside oak-recruitment (regeneration) is also a problem: for some unknown reason, acorns are not producing oak trees anymore - as of twenty years ago, no one knew why).

And should I add visitors? During and immediately after lock-down there was/seemed to be a change of behaviour; maybe it was just what had become normal behaviour but was being reported more often: people seemed to be visiting beaches, nature reserves and national parks and just (seemingly) trashing them. There were reports of carpets of litter being left on beaches and heathland, and volunteer litter pickers being sworn at if they moved in too soon to tidy up; and scheduled plants on triple s i's being trampled and those manchester moorland fires, and countless smaller fires starting from car-park barbeques. Just looking at some that I bookmarked at the time I have: Coronavirus: Lake District clean-up group launched to tackle 'awful' littering, Lake district rubbish makes me want to cry, Borrowdale's Stonethwaite Campsite shuts after 'Covid campers' litter, Coronavirus: Day trippers told to stop littering Yorkshire countryside, Jurassic Coast beach crowds 'showed shocking disregard for area', Nature reserves 'trashed' after lockdown easing,("More than 20 nature reserves have been trashed as anti-social behaviour hit "unprecedented" levels following the easing of lockdown"), Bournemouth beach: 'Major incident' as thousands flock to coast ("33 tonnes of waste was cleaned up along the coastline on Thursday morning, along with eight tonnes collected between the piers on Wednesday."), Coronavirus: 'The sheer amount of beach rubbish is colossal' (Great Yarmouth). We spoke about it here: I seem to remember someone starting a thread on the subject: I also seem to remember it was somewhat de-railed. So tourism/ammenity is out unless you add in the cost of wardens to clear up after the visitors that have become too used to having their rubbish tidied up for them after they leave their table at 'macdonalds*'.

So er yeah. S'a bit more complicated than that. Sorry for the generalities there's much , much more detail that could be added and even allowing for that, sorry for the loser length post but idle thoughts upon a lifelong interest, you know how it is hope there's not too much personal prejudice crept in; sorry too if it's all out of date now, I hope it helps, but I enjoyed writing it: it's years since I've had the opportunity to do something like that. I just sort of started and, bleurgh, couldn't stop; and then I kept adding to it, couldn't leave it alone: I may have wandered, forgive me.
Happy woodland days
TB

[Bird on a Fire]

A bit on this in the IPCC WGII report out today (via Carbon Brief):

Keeping “existing natural forests” standing and sustainably managing “semi-natural forests” “is a highly effective NbS”, the report says with high confidence.

Protecting natural forests currently contributes between 5-7bn tonnes of CO2 per year (GtCO2/year) to climate mitigation efforts, it estimates.

The assessment states with high confidence that reforestation “can be one of the most practical and cost-effective ways of sequestering and storing carbon”, while also protecting and helping biodiversity recover – particularly if carried out with “climate-resilient native or geographically near species”. It can also help improve water supply and quality in ecosystems and reduce the risk of floods and soil erosion.

Wildfires, droughts and pest outbreaks count as severe disturbances that can cause tree mortality, pushing stored forest carbon back into the atmosphere, the report notes. These disturbances are on the rise because of climate change, prompting a “need to adapt”.

Ecological restoration with diverse species “rather than monoculture plantations” can help reduce these risks.

The report notes with very high confidence that mono-culture plantations that fail to plan for their host landscapes, do not “meaningful[ly] engage” with Indigenous and local communities, or seek their “free prior and informed consent” can “present risks to biodiversity, rights, livelihoods and wellbeing, as well as being less climate-resilient than natural forests”.

In addition, the report warns with high confidence that afforesting savannahs, natural peatlands and other areas that do not naturally house forests “damages biodiversity and increase[ s] vulnerability to climate change…so is not a Nature-based Solution and can exacerbate greenhouse gas emissions”.

There's lot of forestry on peatlands in the UK, of course.

Cities are also a good place to plant them (though many parts of the UK are doing the opposite):

Street trees, green roofs, green walls and other urban vegetation are among the strategies it lists that can reduce extreme heat by cooling private and public spaces.

Outdoor green spaces may also slightly reduce indoor heat risks and contribute to lower energy costs, it says. Studies assessed show that homes with shade trees “in cities where air conditioning systems are common can save over 30% of residential peak cooling demand”.

There is robust evidence that “urban parks and open spaces, forests, wetlands, green roofs and engineered stormwater treatment devices” reduce stormwater runoff, surface flooding, and contamination of runoff by pollutants.

https://www.carbonbrief.org/in-depth-qa ... -the-world