What is Urban Sprawl? Why is this Relevant to London?

-This is the Growth of Urban Areas into the Surrounding Rural Areas - Its just Expanding the City as because Demand Increases for Housing -Since 2013, the House Buildings have Tripled which has lead to Urban Sprawl -This Urban Sprawl has lead to Habitats being Destroyed and have the Home Prices for nearby Rural Areas to go Up, as its near the Bustling City