Do trees make people happy? Well yes, I think most people subjectively just have a sense this is true. But for the cynics out there, there is also hard scientific evidence. People have tried all sorts of economic approaches – correlations with real estate markets and willingness-to-pay surveys – for example, to try to estimate the value people place on trees. (Can you measure happiness in dollars? The average man on the street might say no, but the average economist might say it’s the best of many imperfect options for measuring value.) Medical researchers have tried having people walk around cities with brain scanners on their heads. This is a new one to me though – correlating tree coverage with antidepressant prescriptions. And the correlation is there.

Growing evidence suggests an association between access to urban greenspace and mental health and wellbeing. Street trees may be an important facet of everyday exposure to nature in urban environments, but there is little evidence regarding their role in influencing population mental health. In this brief report, we raise the issue of street trees in the nature-health nexus, and use secondary data sources to examine the association between the density of street trees (trees/km street) in London boroughs and rates of antidepressant prescribing. After adjustment for potential confounders, and allowing for unmeasured area-effects using Bayesian mixed effects models, we find an inverse association, with a decrease of 1.18 prescriptions per thousand population per unit increase in trees per km of street (95% credible interval 0.00, 2.45). This study suggests that street trees may be a positive urban asset to decrease the risk of negative mental health outcomes.

And in other urban tree news, you can collect ginkgo berries, take out the nuts, roast them and eat them. The only problem being that they stink to high heaven and are mildly poisonous. Ginkgos are very interesting trees though, sort of an ancient cross between trees and ferns if you believe this article.

Believed to be truly indigenous to only a single province in China , this 270 million year old species belongs to an ancient lineage of species that have since disappeared for one reason or another over the past few millennia, making Ginkgo biloba (known as a ‘living fossil’) the sole extant representative of what was once a vast and diverse group of organisms. In fact, the ginkgo tree is so unlike any other living plant species that this tree has it’s own genus, family, order, class and division. To put this into terms that may be easier to conceptualize: the only thing that ginkgo trees have in common with other plants is they are also plants. This means that pretty much everything about their genetic make-up, physiology, general behavior, reproductive strategies (including their mobile sperm; a trait particular to ferns, cycads and algae) and even their ability to photosynthesize is anywhere between slightly-off to fundamentally different from any other living plant. Oh, and you can eat it’s seeds…

It’s a bit of a messy operation collecting the seeds which are often produced profusely by female trees and lie unmolested by fungi, insects or most pests of any kind save for some adventurous squirrels which occasionally eat the seeds. I find some rubber or latex gloves and a plastic bag are your best bet for collecting the seeds in addition to some grubby clothes that you don’t mind smelling cheesy for a little while. The scent from the fruit tends to linger when it gets on fabric or clothing and so you might want to try extra hard to remember not to wear anything that you are particularly fond of when engaging in the participatory act of ginkgo seed collecting.

I think it’s cool that some people do this, but I personally am not going to take up this hobby right now.