This week the Guardian reconstructed the dawn chorus of 1976 Britain to make audible how many songbirds we have lost in fifty years, back when tens of millions more were still in full voice.

Science has a name for this. In 1995 Daniel Pauly called this the shifting baseline syndrome: a psychological and sociological phenomenon where each new generation accepts progressively degraded environmental conditions as the “normal” state of nature . My baseline sits lower than my parents’, and I never noticed, because I calibrate on what I know. My children’s is lower again. The same applies for bird sounds.

This year we installed passive acoustic monitoring in our food forest Vuurpad: recorders that capture sound continuously, with BirdNET (a neural network trained on thousands of species) for identification. The next step is a reconstruction reaching back to 1968, my birth year. It is not a recording, but a back-projection. The audio is derived entirely from (part of) my own original recordings, and it very likely underestimates the richness of he sounds that were to be heard in 1968.

Dutch farmland-bird populations have fallen by more than 70% since 1960, driven mainly by agricultural intensification and the loss of hedges and other small landscape features. The skylark was still among the country’s most widespread and abundant farmland breeders around 1975, then declined sharply. For the farmland–woodland edge here in South Limburg, the historical soundscape could plausibly have carried a far stronger presence of farmland and hedgerow birds such as skylark, yellowhammer and tree sparrow. The positive news is that local restoration and less intensive management can produce strong, site-specific recoveries as well.