OK, so hate is a bit of a strong word.

I'm sure they're kind to their mothers, save lots of birds, are upstanding for the national anthem, etc.

But what I find more than a little disdainful is the mind-bendingly bizarre value system that sees the organisation, and others like it including WWF-UK and the National Trust, lobby against the proposed Severn Barrage.

The RSPB and seven other green groups have this week released a report they commissioned from consultancy Frontier Economics which concludes that the proposed Severn Barrage would prove significantly more expensive than other forms of renewable energy and could not be justified on economic grounds.

They appear to have decided that the government will play deaf to their pleas not to evict 68,000 odd birds by flooding their homes and have instead argued that the project should be blocked for economic as well as ecological reasons.

It is hard to know where to start when assessing how wrong headed all this is, but if the RSPB and co want to talk economics let's start there.

The fact is that all forms of large scale renewable energy projects are "exorbitantly expensive" when compared to fossil fuels and that is not about to change any time soon. You can argue that we should ditch the Severn Barrage project in favour of other forms of renewables on cost grounds, but if cost is the only consideration then you should ditch all renewables in favour of coal.

Furthermore, if we are going to focus on cost the most cost-effective form of renewable energy currently available is onshore wind farms, which, you've guessed it, have also faced occasional opposition from the RSPB for shredding birds and destroying habitats.

In fairness to the RSPB, it has been far more supportive of the wind energy sector than nimby-motivated countryside groups and has supported the development of many wind farms, including the Thames Array. But it also recently secured victory in its campaign against plans for a 181 wind turbine development on the Isle of Lewis in Scotland, claiming it would damage ecologically important peatlands.

It is worth observing that if its sole concern when it came to the UK's renewable energy mix was cost then the RSPB would have supported the Lewis wind farm and opposed the far more expensive offshore Thames Array.

The fact is that cost is not the only consideration when looking at the pros and cons of the Severn Barrage. Yes, it would be far more expensive than other forms of renewable energy, but it would also deliver significant benefits: it would generate almost five per cent of the UK's energy in one hit at a time when attempts to build countless smaller projects are constantly hampered by local planning problems and the clock is ticking on the EU's renewable energy targets; it would provide a genuine flagship tidal energy project, underlining the UK's positions as a leader in marine energy and providing it with invaluable technologies and expertise that could be successfully exported; and it would provide a far more reliable source of energy than those turbines and solar panels that the RSPB et al are now advocating, but are at the mercy of changing weather conditions.

These benefits will have to be weighed up against the financial and environmental costs and it is exactly this work that the government is undertaking right now through its feasibility study.

Let's not kid ourselves here, the opposition of this coalition of green groups to the Severn Barrage is driven not by concerns for the tax payer but by their fears for our feathered friends - and it is this that I find so perverse.

Just so we're straight I do not hate birds. As a country boy born and bred I am well aware of the huge ecological, aesthetic and economic value of the biosphere - and that is precisely why I am so in favour of large scale renewable energy projects.

Climate science tells us that if by the end of this next decade we have not made significant progress towards decarbonising the economy then every single one of the habitats that wildlife groups campaign to protect will be irrevocably damaged. Yes, 60,000 birds could lose their homes as a result of the Severn Barrage, but if all such projects are stopped or even slowed down by concerns over local wildlife then the long term impact on the biosphere will be catastrophic.

And let's remember when we talk about the biosphere we are talking about human beings too.

It is hugely simplistic to try to position the Severn Barrage as a debate over the loss of wildlife in the Severn Estuary against the loss of human life in countries already being impacted by climate change, but at its most fundamental level that is what we are talking about.

It is hard to completely shake the feeling that somewhere along the line the opposition to many renewable energy projects undertaken in the name of wildlife conservation is underpinned by a sense that animals are more important than people. A view, which personally, I can't even begin to comprehend.

I spoke with Martin Harper, head of sustainable development at the RSPB, yesterday and he argued vehemently that the organisation "passionately supported renewable energy". It is just that it believes there are more sustainable options than the Severn Barrage and that the low carbon energy revolution that is required should be "achieved in harmony with the natural world".

But while that is all well and good in an ideal world, we have just 10 to 15 years to deliver significant cuts in carbon emissions and the sad truth is that to achieve the requisite changes at the requisite scale we will have to be far less precious about those still relatively small parts of the natural world that will get trampled on in the process. The RSPB and groups like it claim they support more sustainable renewable energy developments, but even where they do not explicitly stand in the way of projects the hugely onerous and long winded environmental assessments that developers are made to carry out only result in further delays.

If you accept the analogy that the fight against climate change needs to be treated with the same urgency as a World War - as many environmental groups and politicians do - then what opponents to projects such as the Severn Barrage are suggesting is that you call a halt to a battle for fear that some moorhens end up as collateral damage. Personally, I'm willing to sacrifice the birds.