Biodiversity Audit 2021

Following the results of our 2021 Biodiversity Audit, Wolfson's grounds are a force of nature in our fight for sustainability. 

By Sir Tim Hitchens

We all know that Wolfson College, built in the early seventies, is architecturally wasteful of energy. That’s why we are in the midst of our Zero Carbon project. Our ambition is to reduce our estate’s carbon emission by 75% by this spring. Were we to do nothing we would emit 24,000 tonnes of carbon over the next twenty years. Triple glazing, installation of air source heat pumps, converting all our lights to LED, extending our rooftop solar panel farm, sourcing our electricity supply from renewable sources, and in time connecting the energy we collect from our panels to the latest battery technology: all these will allow us to make important reductions over a short timeframe. We should make big strikes towards zero carbon in scopes one and two (the carbon we emit, and the carbon emitted by our energy suppliers), and towards carbon neutrality in scope three (the emissions from our supply chain.) 

But there’s another side of the story, the credit side, which we’ve all known about but found harder to quantify. Just how much is our estate naturally good at carbon capture and storage? Last summer, for the first time, we undertook the research, and the results, available here on our website, are remarkable. 

As part of a group of Oxford Colleges keen to improve biodiversity across the Collegiate University, we ran a series of measurements and experiments to track precisely what our contribution to environmental health is. A selection of students, Fellows, families and friends undertook a biodiversity audit in June and July. It showed how much we are taking carbon out of the environment naturally; hinted at how biodiversity helps cushion the worst of the climate change effects; and was a reminder of how important for our wellbeing biodiversity around us is. 

First, we looked at every single one of our 475 trees (second only in Oxford to Magdalen College, with its deer park) and measured their width and height. This gave us a calculation of how much carbon they were storing and capturing. Trees are nature’s most effective carbon capture and storage. We also identified that we have 128 different species of trees growing in our grounds. Across 3.3 hectares, they store over 98% of our carbon in their trunks, branches, leaves and roots – about 428 tonnes of carbon in all. 

We then undertook a number of surveys of our earthworm population. Earthworms are an excellent indicator of the health of soil (if it is too compacted, it will neither capture as much carbon nor provide a home to as many earthworms). The deeper they are, the better the soil health. 85% of the earthworms we surveyed are soil feeding, 15% are surface feeding, which is good. But we did not identify any deep living earthworms. 

We used satellite data to analyse our land use, including the sites of special scientific interest which are our meadows on the other side of the river Cherwell. Of our 14.27 hectares (35 acres) of land, about 30% is the built estate, with the remainder being grounds and garden. 3.3 hectares are trees, 4.03 are meadow and uncut grass, 1.25 are wetlands, water meadow and water, and 1.38 are mowed lawn. 

And we know that there is a direct connection between biodiversity and sustainability, so we used experimental techniques to assess our insect and bird variety, strong indicators of our biodiversity in general. At the time of counting we had at least 49 different bird species, including seven RSPB Birds of Red Conservation Concern. We identified 1394 insects, the third ranked among Oxford colleges, and the allotments at College were especially rich for pollinating bees and wasps. 

All told, these calculations suggest that in 2021 the College is taking around 434 tonnes of carbon out of the atmosphere through our natural habitat, to set against the annual average of 1,200 tonnes we would have been emitting from our main estate over the coming twenty years if we had not started on our Zero Carbon works in August.  We need to check our calculations once the works are finalised, but if we have reduced our annual emissions from the main estate by two-thirds, that would suggest an average carbon emission of 400 tonnes (one third of 1,200), less than the 434 tonnes of carbon we are already storing annually through our natural environment. At this stage we are only talking about the main estate, and scopes one and two, but this would be a fascinating result. 

Our impressive biodiversity suggests that this natural habitat is more sustainable than most around Oxford, provided we continue to cherish – and extend - it. 

So, while our Zero Carbon estate project moves to reduce our main estate emissions to zero; as we deepen our scope three work, to introduce electric vehicles, reduce meat consumption, and look at offsetting; and as we all, collectively, take steps in our private lives to reduce our carbon footprint; we can also be pleased that the natural environment of our College is giving us a helping hand, and actually taking carbon out of the environment, not simply emitting less of it. 

I’m glad you’re all part of this important experiment. Wolfson, naturally.