The competition for land in some densely populated countries has further meant that underground mining is the only viable alternative. Such developments have halted the growth of open pit mining and it is projected that the present ratio 1:6 underground to open pit mining will continue in the medium term.
Por favor, me podrían ayudar a traducir la parte que esta en negritas ya que no entiendo bien lo que quiere decir.
De antemano gracias