Data-driven allotment: GRI 13.3 - Biodiversity

Introduction

This is one of a series of posts about one of my favourite topics - my allotment! And more importantly, how green it really is, using a selection of topics from GRI Standard 13: Agriculture, Aquaculture and Fishing Sectors.

I am a big believer in learning by doing, so when the Global Reporting Initiative released its standard for the agriculture, aquaculture and fishing sectors in 2022, I thought the best way of getting to grips with it was to try to apply it to my allotment. As I’m sure you can imagine if you’ve ever reported under the GRI standards, this was a challenging task. Firstly, quite a few of the topics simply aren’t applicable (or ‘not material’ as the Standard itself puts it), For example, I don’t keep livestock on the allotment so I don’t have anything to say about 13.11 - Animal health and welfare. Others I can address, but only indirectly, so whilst I don’t use pesticides, I can think about 13.6 - Pesticides use through the lens of ‘organic’ alternatives to conventional pesticides. You can find a complete list of the standard’s topics and which ones I have decided are immaterial or of limited applicability here.

Perhaps unsurprisingly, given my interest in horticulture and food systems, I am also interested in the ‘business’ side of the allotment - i.e. doing a very basic cost/benefit analysis. As I worked through the topics, it also became clear that this information was relevant to topics like 13.3 - Food security and 13.21 - Living income and living wage. Ultimately, I’ve ended up recording both environmental and financial data, some gathered myself and some from reliable sources like the Met Office and the Soil Association. The different types and sources of data are summarised here.

Whilst I have made every effort to be as thorough as I can be about this process, it’s important to remember that this is just an intellectual exercise for me, and I make no claim to the sort of scientific rigour that large food-producing businesses have to put into their reporting.

On to the interesting bit…

This month’s focus is GRI 13.3 - Biodiversity. Alongside Disclosure 3-3 Management of material topics, there are four specific disclosures required by the Standard. These have very long names, and I won’t repeat them here since they aren’t really particularly relevant to what happens on my allotment. Biodiversity is a notoriously thorny thing to measure - do you simply pick a day and see how many different species you spot on that day? This kind of sampling approach seems to be the most commonly used, but it’s fraught with all sorts of challenges when it comes to collecting the samples.

Interestingly, I’ve never tried it on my plot, and I’m not even sure what use it would be - anecdotally I can tell you that my plot is visited by magpies, robins and pigeons, and also – probably as a result – lots of domestic cats. But what about insects and other invertebrates? I suppose I could try setting up a moth trap overnight and seeing what shows up, but to be honest, I’m not sure if I would really understand what I was looking at. And what about microbial biodiversity? There are highly sophisticated techniques for getting accurate measures of these things – for example, a speaker at a recent EWT Chelmsford talk (The Unnatural History of Rivers) mentioned that they use DNA analysis techniques on water samples to determine the genetic diversity of rivers. This is obviously way beyond my capabilities, and overall, getting a really accurate measure of the biodiversity of such a small piece of land as my allotment is, with current capabilities, challenging.

And yet, with the entry into force of the biodiversity net gain legislation in England and Wales (and variations of it in Scotland and Northern Ireland), this is something that people much smarter than me have been thinking about. And I happened to hear in a recent RSK webinar (I forget which – it was one of the First Thursday Club series) about something called the Small Sites Metric, a tool designed to help developers assess the impact of their development on biodiversity (all developments must now achieve a 10% net gain for biodiversity). Despite being for ‘small’ sites, it’s still far too complicated for my allotment, but the basic principle still intrigues me.

Instead of attempting to define biodiversity by the number and frequency of individual species, the metric focuses on the actual habitats, with the assumption that if there is habitat, wildlife will arrive to occupy that space – ‘If you plant it, they will come,’ you might say. Of course, it’s not just about planting. The metric covers 14 ‘baseline broad habitat types’, including arable land, hedgerows and watercourses. There is a limited number of these habitats on my plot - if we ignore for a moment the category for simply ‘cropland - allotments’, it would probably be entirely defined as ‘cropland - non-cereal crops’, so of comparatively little use. But it did get me thinking…

Structural changes – perennial planting

I love bees - I mean, who doesn’t? (Unless you’re allergic, of course.) Every year I try to dedicate part of my plot to a wildflower mix that can keep my little buzzing friends well-fed, and also coincidentally helping to pollinate my crops, of course. On a warm summer’s day, I can genuinely pull up a chair and just sit and watch them flitting around the mini-meadow for longer than I probably should. It’s in moments like that that I am at my most biophilic.

But bees and other pollinators, and indeed birds, don’t only need food during the summer - they also need a winter supply. Yes, I know, many bees hibernate, but there is other wildlife awake during the winter, and they are just as vital. This is a bit of a challenge, though, for allotments, because they mostly follow annual (or in some cases biennial) planting patterns, whereas the types of plant that provide wildlife with sustenance through the winter are generally speaking perennials. It is, unfortunately, just not practical to keep moving perennial plants from one bed to another every year. I could potentially use big pots, but they’re heavy to move and require more care than plants in the ground.

So how do we solve this problem? Well, I could permanently give up some of my annual planting space. And to an extent I have done this. If you’ve read previous posts, you might know that the plot that is the focus of this blog has a small walnut tree at one end. I didn’t put it there, and it wouldn’t have been my choice, but there’s no way of getting rid of it now. Underneath the tree is my ‘home for retired strawberries’ - the older plants whose glory years have passed but which may have a few strawberries left in them yet. I’ve started interspersing these plants with annuals, like foxgloves and borage. They compete with the strawberries of course, but then I never expected much of a crop from them anyway.

But I think the time has come to be more ambitious. One thing I noticed about my ‘main’ plot (i.e. the original one, not the one I focus on here), is that there’s a part of it I don’t use very much. The top half of the plot is laid out as 8 rows of 2 raised beds, with a central walkway down the middle, but in many ways, the central walkway is impractical - it’s too narrow to get a wheelbarrow down, and I often put a single net over both beds in a row blocking the path anyway. So my plan for this year is to enclose that central walkway by filling in the gap between the beds and then using that as a permanent plot where I can plant my winter-flowering perennials and other companion plants.

I haven’t quite decided yet whether I want to absorb the entire walkway, or just fill in the gaps between the beds, leaving a long walkway between rows, but I’m excited by this idea! Not only does it give me more space to help make a positive contribution to biodiversity, but it will also allow me to get rid of metre-upon-metre of that awful black weed suppressant fabric that I put down because it’s what everyone does and have since come to hate. Instead I will fill it with snowdrops, hellebores, winter primroses and crocus bulbs, and all the other perennials that I have long wanted on my plot but couldn’t quite find space for. More research is needed – I’m thinking I need some sort of winter-berry-bearing plant for birds, suggestions on a postcard please.

Creating homes for fauna

I said that my plot is primarily cropland, and that’s true, but there is an area that you might call a hedgerow, after a fashion. In fact, the small sites metric wouldn’t call it a hedgerow – there’s a whole section on what category to put hedgerows under based on what kind they are. It’s essentially a bit of land between my row of plots and the next row that I think must have been left out of the site plan to help keep the plots in straight lines. I get the impression that it may once have been communally cultivated – there’s certainly a couple of fruit bushes in there that I don’t think could have occurred naturally. They’re mostly overrun now with nettles and overshadowed with some small trees that have grown up in the meantime. It would take serious effort (and equipment) to restore it to traditionally ‘usable’ allotment land.

That doesn’t mean it serves no purpose at all, of course, Nettles, whilst annoying, are useful for many types of insect, and in fact may even be useful to me if I ever get round to reading up on how to spin them into twine. And whilst I haven’t seen any nests in the trees, the birds certainly do like to sit in them whilst I’m working – there’s a least one robin that will sit there watching me weeding a bed or digging up potatoes, presumably hoping that I’ll expose some tasty worms for it to snack on. There’s also a monster of a bramble bush (actually, probably two or three by now) that creates all sorts of nooks and crannies for wildlife.

And whilst I am generally happy to leave this area to ‘do its thing’, I have tried to help. I’ve put a small bug hotel amongst the thicket, and I pile up old branches on the rare occasion I get them. This year I’ve also bought some little birdboxes, or rather bird baskets(?). They’re made of woven strips and hang off branches, as I don’t think I would be allowed to nail actual bird boxes to the trees. I’m also planning to invest in a hedgehog house this autumn. I like hedgehogs almost as much as bees, not least because they eat slugs and snails. I am wary about putting food down for them, though. I have had a least one mouse on the plot, which nibbled its way through my cardboard seed boxes, which is why my seeds now live in sealed plastic tubs. But I can at least provide a bit of accommodation, again in the hope that ‘if you build it, they will come’.

Crop choice/rotation

Whilst the structural changes mentioned above relate to more ‘permanent’ changes to my plot, there are also changes I can make/have made to my planting habits. There are two issues combined into one here - the biodiversity of the types of veg I grow and the biodiversity within those veg. According to the standard:

Biodiversity can be adversely impacted by monoculture. Growing the same crops or rearing the same animal species year after year may increase production but it also decreases agrobiodiversity on farms and plantations and can compromise biodiversity in adjacent environments. In crop production, continuous monocropping can result in a buildup of pests and diseases, usually requiring higher volumes of pesticides, which can be toxic to many non-target species, including pollinators.

This issue is, to an extent, naturally counteracted by the way allotment-growing normally works - allotmenteers very rarely practice monocultures, simply because that’s not the purpose of an allotment. Nobody wants to live off carrots all-year round, after all. The issue of disease build-up can be a problem, and it’s the main reason I have a four-year rotation cycle (legumes-brassicas-roots-potatoes). It’s also better for the soil - more on that in a later post.

But there’s also the issue of biodiversity within crops. Standing in front of your local garden centre’s seed packet display, it can seem like there’s endless types of peas and potatoes and carrots and so on to choose from, but the varieties grown commercially these days only represent a very small fraction of the varieties that have existed historically. And just some of those ex-/non-commercial varieties are preserved and cultivated by the Heritage Seed Library, which I am a proud member of. In their own words, “The Heritage Seed Library (HSL) maintains the national collection of heritage vegetables and aims to conserve vegetable varieties that are not widely available, sharing seed with our members to grow and enjoy.”

This year, for example, I have received non-commercial varieties of peas, onions, leeks and French beans, which will go into my rotation and boost its biodiversity. You could perhaps argue that the wildlife that hopefully comes to my plot will not notice the difference between my heritage Essex Pea Bean French beans and my normal Cosse Violette French beans, and you may well be right. But maintaining a living stock of these non-commercial varieties does ensure the largest possible variety in the gene pool of the vegetables that we eat, and they may have characteristics that we need to breed back into those commercial varieties as our climate changes, boosting our food security (again, a topic for a future post).

One final adjustment to my rotation that I am planning to have a got at this year is bi- and poly-cropping. I was inspired by a talk given by Wildfarmed at the Writte Farmers Club Conference on how crops can be combined with either other crops (e.g. wheat and broad beans) or with cover crops (e.g. brassicas and herbal leys) to improve yields whilst also restoring the soil and providing pollinators with larger and more diverse sources of food. I’m also intrigued by the idea of intercropping flax, as I’d love to have a go at spinning my own linen. This process might sound like companion planting, but it’s rather more intense than that, and to be honest, I have struggled to find any resources about doing it at a micro-scale. But fortunately, I love to experiment, and at least I’ll have something interesting to report on next year!