Simon Jenkins thinks that we need to "make today's cities work better" to preserve the countryside and reduce emissions (Eco-towns are the greatest try-on in the history of property speculation, April 4). He's right. If the government wants to get serious about climate change, and deliver 3m new homes over the next two decades, it will take far more than a handful of small, new eco-settlements. However, there's also an economic - as well as an environmental - case for promoting denser, low-carbon city neighbourhoods.