91热爆

Chalk. Such cliffs provide housemartins with their natural home. They had to wait for us to arrive on the scene before they could nest on the artificial cliffs of our houses. When our ancestors did get here, they left their own postcard to the future, celebrating the 'fertiliy of the land'. But that fertility came only after they'd set up a working relationship with the chalk downs that actually maintained them as downs. Grazing by sheep and rabbits favours particular plants - and in turn particular insects, like ants and butterflies. For all its early life the Adonis blue butterfly is protected by ants. Only as it breaks out of its chrysalis and climbs aloft to spread its wings, is it freed of their helpful attentions. It's a great rarity among other butterflies that are such a lively part of the colours of a chalk grassland in summer. It's a landscape that inspires.