Since the 20th century the spread of intensive farming techniques (including sometimes heavy use of nitrate fertilisers) along with the possibilities offered by heavy equipment to transform limestone pavement into pasture has posed new challenges for the ecosystem and its diversity. Research conducted in the 1990s suggests that by the end of that decade the area of limestone pavement had halved since pre-Famine times, c. 1840, while from the 1970s to the 1990s alone, about 4% of pavements were converted into pasture or covered by roads.