I was reminded by Facebook yesterday that I had posted a picture of my sunglasses 5 years ago. One balmy June evening, I had dug my bike out from the back of the shed, brushed off the cobwebs and set off with my sunglasses on to protect me from flying insects. As a child of the 1970s this was normal behaviour; the evening air would be thick with insects and a bike ride risked a fair chance of swallowing a few and getting them in your eyes. But when I returned home, my glasses were completely clean – not a single insect. As someone who reacts strongly to insect bites, this should have been good news, but it really isn’t.

2019‘s State of Nature report reveals just how catastrophically the UK’s biodiversity is plummeting, with 41% of our species in decline since the 1970s. Creatures needing specific habitats, such as specialist butterflies, have decreased even further, by 68%. Living in the country, you are more aware of the landscape around you and the incremental ways that wildlife has come under siege from us in all directions. The figures support my experience and the future looks grim. I assumed this was a one-way street and that our insects – and therefore we ourselves, as we depend entirely on them for our survival – are doomed.

Insects are mostly small and we don’t notice them. But there are 1.4 billion of them for each human on the planet. If humans disappeared, nothing disastrous would happen, but if the insects die out, it’s a major catastrophe. Insects are the major food source for many birds, fish and mammals (including more than a quarter of us humans), they pollinate many of the world’s plants, including human food crops, and they break down matter- without them we would be buried in debris and rotting matter.

When I visited my first beaver wetland and hope began very tentatively to grow again. It was like travelling back in time – not to the ever-sunny 1970s of my childhood but to a primeval landscape where nature was truly abundant and almost overwhelming. Insects flitted and buzzed in all directions, birds fluttered and dipped from branch to branch, fish plopped continuously in the pools around me and the vegetation grew thick and lush from ground level into the tree canopy. I could hear the sound of someone crunching something very close to me and, parting the thick marsh grasses, saw a beaver feasting on the shoots of new willow growing upwards from the trunk of a coppiced tree. To be so close to such a wild animal is a thrill and a privilege; my heart sang.

Woodland Valley Farm above the frequently flooded village of Ladock houses a beaver enclosure run as the Cornwall Beaver Project in partnership with Cornwall Wildlife Trust. The farmer whose family has worked this land since 1960 is Chris Jones, director of Beaver Trust. He brought the beavers in originally to help prevent flooding downstream, but now he believes beavers offer the UK a far greater opportunity; to restore our 300,000km of rivers to ecological health by helping to clean the water and restore biodiversity. Since bringing these remarkable animals to his farm in 2017 he has seen 6 new birds, 3 new mammals, increased numbers of amphibians and too many insects and plants to count. The amount of water stored on site against drought has more than doubled and his cattle can enjoy grazing in the woodland.

The Eurasian beaver, which was native to Britain and once widespread, are bigger than you might expect – around 25 kilos or the size of a spaniel – and are the second largest rodent in the world. They are also heavyweights in our ecosystem. As a keystone species, when they disappear, a lot of other wildlife goes with them. And when they return, it comes back. The scientists will be shouting now at this simplistic view, wanting nuance and caveat. But this is a blog, not a scientific paper – and plenty of those will tell you the same thing.

Beavers are agile in the water but slow on land and make easy prey, so they make their homes or lodges from thickly woven branches and a safe underwater entrance. If the water is not deep enough to allow this, they dam it until the level rises. Working mostly at night, they fell trees with their bright orange, self sharpening teeth, and drag the timber (even floating it down special channels from further away) to where it is needed, keeping the leafy part for food. They only eat plants, so fish tend to thrive in the varied pools, channels, dams and thickets of a typical beaver wetland. Studies are going on right now to work out how much carbon is stored in those dams, as they filter out pollutants and make Ladock’s water cleaner.

At this time of flux and fear, we sit staring at the targets of the Paris Agreement and wondering how we are going to reduce our per head carbon emissions from 8.9 tonnes to the absolute maximum 2.4 or much safer 0.8 tonnes per head that we need to achieve. But it is also a time of possibility – many people during lockdown have experienced a greater appreciation of nature. We have properly heard birdsong for the first time. We have gone for long, unhurried walks in our own neighbourhoods and seen the wildlife around us flourish without our pollution and traffic. We have seen the clear skies reclaimed by the birds. It would seem sad to lose that again and we can choose not to. This Environment Day, think about what is really important, get outside, listen to the birds, and make your choice.