Croydon's open spaces tended to be thought of as "development opportunities" rather than land on which people's livelihood directly depends. Without the working woodlands, agriculture and grazing animals of the past, many areas became neglected. Ponds dried up, streams were banished underground, grassland and heathland became covered with scrubby trees, and woodlands became dark, forbidding places. The plants and animals that had become so dependent on these earlier habitats also became rarer or even extinct in Croydon. In addition nibbling rabbits were much reduced in numbers due to myxomatosis in the 1950s. According to Friends of the Earth we have lost in the UK, 30-50% of ancient woodland, 95% of flower-rich meadows, 80% of chalk grassland, and 40% of lowland heath. In Croydon these losses have been mainly due to housing development and scrub invasion.