If we ask ourselves what has been lost, that we really care about, in the last 50 years, what has gone from the natural world in Britain that was special and is now much missed, we might come up with many different answers.
Some people would undoubtedly say the red squirrel, stunningly beautiful for a small mammal, in fact almost feminine in its beauty, and now driven to extinction south of the Lake District (apart from a few corners) by its grey cousin. Others might instance the cornflower, that heart-stopping bloom of the crop fields, which was of such an intense deep blue that it almost seemed to be radiating heat. Intensive farming did for that.
Butterfly enthusiasts might mention the large tortoiseshell, handsome as a lion, which wasn't common but still appeared to be flourishing in a few places after the war, and then was suddenly gone (nobody really knows why). And many bird lovers would doubtless bring up the red-backed shrike, the magnificent mini-predator that was still pretty visible half a century ago but then dwindled to nothing by 1990 (although the odd pair still breeds here).
You could lament the disappearance of any of those, and if you put them together, you're embarking on a true litany of loss. But although I regret them all as keenly as the next person, they're not what I mourn most. I mourn the loss of abundance.
Do you remember when on warm summer nights, if you drove through the countryside in a car, you would drive through snowstorms of moths, so thick that at the end of the journey you had to wash the windscreen? Do you remember when in some special places, such as chalk grasslands, butterflies swarmed in clouds? Can you remember skylark song so all-pervading that it seemed to be pouring out of the whole sky in a continuous shower? Can you remember poppies turning a cornfield into a waving scarlet sea?
Perhaps you can't, especially if you're under 40. But if you can, and you have a feel for the natural world, I defy you not to be moved by the memory. Abundance in nature seems to trigger some powerful emotion in us, part delight, part something deeper... perhaps a sense of wonder. Is it a sort of awe at witnessing nature display its power so extravagantly? Encountering it gives us pause; we will nearly always want to speak of the experience to others, later. Yet it doesn't seem to be written about, as a discrete quality. I've never come across a hymn to abundance; I've never even seen the thought formulated. So it has not been seen as a blessing which might be lost.
It actually seems to have been the natural order of things, before the advent of humanity; we think of the cod of the Grand Banks fishery off Newfoundland, once so plentiful it was said you could walk on the backs of the fish; we think of the buffalo herds which once stretched to North American horizons; we think of the passenger pigeon, a bird whose flocks could take three days to pass a given point and may have contained a billion individuals; all decimated or extinguished by mankind.
Being a relatively small island, Britain was affected early, the greenwood chopped down, our bears, our lynxes and our wolves wiped out; then many of the small mammals and birds were extirpated too in the astonishing double pest-pogrom that was undertaken, first by the Tudor parishes, and then by the Victorian gamekeepers (and documented unforgettably by the conservationist Roger Lovegrove in his 2007 book, Silent Fields).
But even though Britain possessed an impoverished fauna and flora compared with the rest of Europe, say, there was still, 50 years ago, abundance to be had. Mayflies hatched on springtime rivers in dazzling swarms. Hares galumphed across every pasture. Suburban gardens were thronged with thrushes. And the moths filled the summer night and the butterflies the summer day, and the larks filled the air and the poppies filled the fields.
All that's gone now. Or, at least, most of it has, largely thanks to the intensification of agriculture, with a few subsidiary causes. You can still find abundance in some treasured surviving habitats – bluebell woods would be one example – but across the land as a whole, there has been a great thinning, a great winnowing out of plenty; there is simply much less of everything than ever there was. And yet people barely realise.
The reason is a peculiar one: each generation takes what it finds around it to be the norm. American biologists have given this phenomenon a name; they call it the shifting-baseline syndrome. Your grandfather saw thousands of skylarks, your father saw hundreds, you have seen dozens and your children will see the odd one, and each of you thinks that that is the way things normally are; that's what the baseline is. But it isn't, of course. The real baseline is "the salmon-falls, the mackerel-crowded seas", as Yeats put it; living things living everywhere in profusion.
We can mourn the loss of our red squirrels and our cornflowers, our large tortoiseshells and our red-backed shrikes, yet it is sometimes possible to bring individual species back. I mourn more for the vanished moth-snowstorms, the vanished butterfly-clouds, the now-unheard showers of skylark song and the forgotten seas of poppies. I mourn the end of abundance, of the natural marvel with all its beauty and all its wonder; for that is gone forever.