The news that renewable power has overtaken nuclear to become the main source of electricity in Scotland is a significant and welcome step towards the Scottish Government's targets on renewables and the long-term idea of transforming Scotland into a 100% renewable nation.

The Government has set itself the goal of generating all of the country's electricity from renewables by 2020 and it remains an extremely ambitious but reachable target for a fairly obvious reason: Scotland is a windy, wave-lashed island and has some of the highest wind and wave energy potential of any country in the world.

However, even with yesterday's news from the UK Department of Energy and Climate Change on electricity generation indicating that Scotland is heading in the right direction on the 2020 vision, there remain some significant obstacles to achieving it and some reasons to be cautious.

One of the most significant is the fact that wind power has reached the point where further development should only be taken forward with considerable care. Many of the most promising - and least controversial - onshore sites for wind farms have already gone, which leaves those that are either in scenic locations such as national parks, or sites where there would be great public resistance. As an alternative, offshore wind farm sites are extremely promising, but this is a sector of the industry that is still in its infancy.

The same problem applies, but even more so, to wave energy, as the recent news about the wave-power company Pelamis shows. The firm has gone into administration after it failed to find a partner that could take its technology into serious production. This is a persistent problem in the sector and demonstrates once again that further investment is needed in renewable technology as well as the infrastructure to transmit green energy to the national grid. The Scottish Government says it regrets Pelamis going into administration, but the Government must also recognise that, if 2020 or anything close to it is to happen, more investment will be needed to grow renewable capacity at a much faster rate.

Until that can be achieved, a mix of energy, including nuclear, will remain necessary and desirable, not least because there are still questions about how renewable energy sources can be made secure and predictable.

Yesterday's figures on electricity show Scotland is taking some major steps towards reducing its reliance on fossil fuels but they are steps on a long road.