Renewable energy resources are growing very fast but countries still must be vigilant to ensure that they continue to expand, the International Energy Agency said Wednesday. The IEA, the energy advisory body to the developed countries, said renewable energy is a key element in meeting increasing demand and balancing environmental concerns. IEA Executive Director Maria van der Hoeven said in a statement that renewables must be stepped up, \"especially given the world’s increasing appetite for energy and the need to meet this demand more efficiently and with low-carbon energy sources.\" Launching a new book, \'Deploying Renewables 2011: Best and Future Policy Practice,\' van der Hoeven said it showed the dangers of relying on traditional energy sources. \"As the IEA’s analysis has shown, without an urgent and radical change of policy direction, the world will lock itself into an insecure, inefficient and high-carbon energy system,\" she said. \"Renewables already play a central role in fostering sustainability and energy security, and their significance will only grow in the coming decades. \"Against this backdrop, Deploying Renewables 2011 provides a major review of renewable energy markets and policies at this critical juncture.\"