The CLA has said the economic challenge facing national parks can only be solved by taking a balanced approach to the economic, social and environmental pillars of sustainable development.
The Association said the long-term future of the landscape within national parks is threatened due to a decline in population, as highlighted in data from the 2011 Census.
CLA Deputy President Henry Robinson said: "The future of our landscapes and the economic success of our national parks are inextricably linked. Looking after the landscape and biodiversity costs money which is why the CLA has long called for a balanced approach to be taken to all three pillars of sustainable development.
"If agriculture, diversification, housing, jobs and tourism are stifled, the landscape that the public so loves will degrade."
He added: "Planning policies in national parks must become much more sustainable to allow change. Otherwise, these areas will continue to be retirement and dormitory zones rather than the living and working communities that they deserve to be."
Find out more about the 2011 Census: Key Statistics for national parks in England and Wales