1/ O.k, so after the #ClimateDebate you're hearing a lot about ambitious proposals for #treeplanting as means of sucking - sequestrating - carbon dioxide from the atmosphere to help get to #netzero emissions. Here's the good, the bad, and the ugly of it... 
2/ First, the good. Yay, trees! We love your carbon-munching, street cooling, insect-loving super powers. Especially in Hackney, where we recently announced largest mature street and parks tree planting programme in the country (there's lots more to come). news.hackney.gov.uk/5000-new-stree…
3/ So, it's genuinely heartening to all mainstream political parties - Labour, in particular - placing tree planting high up their list of priorities. bbc.co.uk/news/election-…
4/ Now for the bad. Numbers, numbers everywhere! While talking tree numbers is a good way of making manifesto pledges 'real' for the public, they don't begin to tell the story of nature-based carbon sequestration. This shows that none of the Parties are doing the hard thinking.
5/ Talking purely in terms in tree numbers is looking at the issue from the wrong end of the telescope. In Hackney, we revisited and overhauled our 2018 Manifesto pledge based on what we wanted to achieve - locked-in carbon, calmer and cooler streets, and increased biodiversity.
6/ In particular, I've been heavily influenced by this fantastic piece of work from @carlyziter & others (who says academics never change anything?) which focuses on the relationship between canopy cover, depaving, and urban temperatures...pnas.org/content/116/15…
@carlyziter 7/ So, rather than put an arbitrary number against the street trees we'll plant in Hackney, we're instead working towards a minimum of 40% canopy cover, beyond which we know we can significantly reduce pressure on medical services and energy demand for cooling.
@carlyziter 8/ Once we knew what level of canopy cover we wanted to achieve on-street, we sat down and costed it. Mature trees - the kind we plant with care on-street - are expensive. There's labour costs, root directors, caging, staking, after-care...
@carlyziter 9/ We realised that, to get to a minimum of 40% of canopy cover on-street, we'd need to invest circa £9m. When you consider that Hackney's Gov't grant has been cut by £140m since 2010, that's a big commitment; a commitment made by people who take the #climateemergency seriously.
@carlyziter 10/ Then we decided what we could afford to invest this term, which is why we've committed to deliver 30% ten year canopy cover by 2022, with 40% cover delivered by 2024. As we currently have 20% canopy cover from 10,000 street trees we know we'll deliver a further 5000 by 2022.
@carlyziter 11/ This all sounds a bit tedious, I know, but it matters. Why? 1 - because it allows us to tell the public a credible story about where our numbers come from, and 2 - because we know it will work to deliver what we want. Evidenced-based policy-making in action.
@carlyziter 12/ The eagle-eyed amongst you may have noticed that, if we're investing £3.8m in the first tranche of 5000 street trees, why are we investing £5.2m in the second phase? Simple, because that phase requires additional physical changes to the public highway. Why does this matter?
@carlyziter 13/ It matters because it illustrates that strategic planting is a lot more than plonking trees in the ground. It requires investment in land acquisition and engagement with land-owners and farmers. Politicians need to reassure the public that they're thinking about the details.
@carlyziter 14/ How can national parties - particularly Labour, from my perspective go about adopting 'the Hackney model' of planning, financing, and planting trees? An excellent place to start would be the @royalsociety and @RAEngNews on greenhouse gas removal...royalsociety.org/topics-policy/…
@carlyziter @royalsociety @RAEngNews 15/ As you can see, @royalsociety and @RAEngNews paper on greenhouse gas removal doesn't talk about tree planting in numbers, it takes a science-based approach to determining how land-use and nature-based approaches can contribute to achieving net zero...
@carlyziter @royalsociety @RAEngNews 16/ ...and, in doing so, it concludes that we need to reforest 1.2m hectares - an area about the size of Yorkshire. Seems a lot, right? Wrong. Yes, it would mean increasing forest cover in the U.K by 40%, but only 13% of the U.K is forested, down from 90% in the neolithic period.
@carlyziter @royalsociety @RAEngNews 17/ So, despite @JustinOnWeb's incredulity in response to @johnmcdonnellMP's tree planting pledges on @BBCr4today, it is desirable, necessary, and *crucially* possible to plant 2 billion trees in the U.K (this is around 30% more ambitious that @royalsociety @RAEngNews proposals).
@carlyziter @royalsociety @RAEngNews @JustinOnWeb @johnmcdonnellMP @BBCr4today 19/ Now for the ugly. While I concur with @GeorgeMonbiot's enthusiasm for natural reforestation and re-wilding, I do so with a couple of qualifications. theguardian.com/commentisfree/…
@carlyziter @royalsociety @RAEngNews @JustinOnWeb @johnmcdonnellMP @BBCr4today @GeorgeMonbiot 20/ First, natural forests take a long time to grow. One of things you may have noticed is that #wedonthavetime. So, while I love and support the concept of rewilding, we also need to to plant for FAST timber growth and reforestation...theguardian.com/environment/bl…
@carlyziter @royalsociety @RAEngNews @JustinOnWeb @johnmcdonnellMP @BBCr4today @GeorgeMonbiot 21/ So, the ugly truth - if you have a view of forests as places of abundant beauty - we also need a LOT of industrial-scale commercial forestry that looks a bit like this (which is still pretty attractive, in my view)...
@carlyziter @royalsociety @RAEngNews @JustinOnWeb @johnmcdonnellMP @BBCr4today @GeorgeMonbiot 22/ So, while people may balk at the idea of commercial foresty, it's also one of the best mechanisms for both increasing forest cover (@andyheald is the man on this) and providing raw materials for timber construction. And what is construction-grade timber, I hear you ask?
@carlyziter @royalsociety @RAEngNews @JustinOnWeb @johnmcdonnellMP @BBCr4today @GeorgeMonbiot @andyheald 23/ Construction grade timber is, on the one hand, a wonder material both strong in compression and tension, and other the other a permanent, useful store of carbon dioxide, since around 70% of timber is locked-in CO2! Why does this matter?
@carlyziter @royalsociety @RAEngNews @JustinOnWeb @johnmcdonnellMP @BBCr4today @GeorgeMonbiot @andyheald 24/ Because, by providing a increasing proportion of the materials that comprise our built environment sustainably-forested, domestically sourced timber can help eliminate carbon-intensive concrete and steel, provide a permanent store of carbon, and drive reforestation!
@carlyziter @royalsociety @RAEngNews @JustinOnWeb @johnmcdonnellMP @BBCr4today @GeorgeMonbiot @andyheald 25/ ...but, don't just take it from me, listen to all-round timber design & construction genius Andrew Waugh of Hackney-based @WaughThistleton talk about the ability of timber to reduce both embedded *and* operational emissions of the built environment: waughthistleton.com/news/18/02/05/…
@carlyziter @royalsociety @RAEngNews @JustinOnWeb @johnmcdonnellMP @BBCr4today @GeorgeMonbiot @andyheald @WaughThistleton 26/ So there it is. The good, the bad, and the ugly of the tree planting pledges being made during #GE2019!
P.S I'm available for birthdays, weddings and bar mitzvahs...
P.S I'm available for birthdays, weddings and bar mitzvahs...
@carlyziter @royalsociety @RAEngNews @JustinOnWeb @johnmcdonnellMP @BBCr4today @GeorgeMonbiot @andyheald @WaughThistleton 27/ Oh, apologies for the typos. I was in a rush!
