DIY can positively influence and improve the eco-friendliness and energy efficiency of your home. Maintaining and repairing is, in principle, an environmentally sound thing to do particularly if you shop online (or by mail-order) to minimise the greenhouse gas emissions resulting from delivery miles.
Unfortunately, on the other side of the equation, many of the materials used in home improvements can be damaging to the environment. This is either as a result of by-products that result from their manufacture, potential damage from their degeneration and disposal or simply because of the materials they use (e.g. rainforest hardwoods). It's always worth finding out where your local building materials salvage yard is, as they can be a great source of recycled materials.
On balance however if you make eco-friendly choices in the materials you use and take care to re-use, recycle or carefully dispose of surplus and waste, then DIY can be beneficial for both you and the environment. Please just browse through the DIY information menu for more detailed information.