Over recent weeks, a number of leading voices in the environmental debate brought you their views on a range of issues in the Green Room.
This week, we have offered the writers an opportunity to respond to your comments.
JEFFREY A McNEELY - Biofuels: Green energy or grim reaper?
I was delighted that my short article on biofuels has generated such a vigorous response - the public clearly has deep concerns about our energy future.
First of all, I focused on bioethanol after reading a report saying that 65 ethanol plants were being constructed in the Corn Belt of the US mid-west, with a combined capacity that the Earth Policy Institute considered sufficient to consume all of the maize grown in the major producing states.
Brazilian cars have been running on bioethanol for years
These are precisely the states that produce excess maize, which is then used as part of the US contribution to the World Food Programme, and distributed to developing countries.
I am very sympathetic to those who believe that such exports may serve as a disincentive for the recipient countries to develop their own agriculture, but the fact remains that some 800 million people in the world remain undernourished and welcome donations of surplus food.
Waste of energy?
Perhaps worse, last November's issue of BioScience reported that the various inputs required to convert maize to ethanol consume 29% more energy than is contained in the ethanol produced.
Ethanol from cellulosic biomass requires 50% more energy than the final product can deliver; and each gallon of ethanol requires 1,700 gallons (6,400 litres) of water and produces 6-12 gallons (23-26 litres) of noxious organic effluent.
Of course, this is just the first generation of just one type of biofuel, and greater investments in second and third generations may greatly improve the picture.
Having said that, I do recognise that bioethanol is simply one of numerous energy options. Biodiesel is undoubtedly a better alternative, and lignocellulosic energy may be even better. And there are more options on the table: methanol, solar, wind, tidal, and nuclear power.
So while my article raised some warning flags about moving ahead too quickly on bioethanol without considering the full costs and benefits, I also believe that a thoughtful consideration of the costs and benefits of all of the energy options are well justified.
This is not anti-capitalist, but the straight-forward application of the precautionary principle, ensuring that we have given careful consideration to the full implications of our investments before we rush ahead to spend them.
Moving ahead too quickly without considering the options is, to use an extreme example, like invading Iraq without thinking about the future implications.
Most energy experts will agree that our first line of response should be improved energy efficiency and conservation. Banning cars would certainly be unpopular but, with appropriate incentives, the use of alternative forms of transport, ranging from walking and cycling to improved public transport systems, would all be relevant in reducing energy demand.
Finally, in the few short months since the original article was published, considerable additional work on biofuels has been done, covering the full range of perspectives.
The expansion of biofuel crops is certainly having an impact on food commodity prices already, which the commodity traders may consider good news. But in many parts of the tropics, land that may be extremely important for biodiversity is being converted to grow bioenergy crops.
Even under the most efficient forms of lignocellulosic processing, we are beginning a massive global experiment whose results are far from certain. Our current way of life is highly energy-intensive, at least for those of us living in cities or developed countries.
This calls for increased investments in research and development to find alternative solutions, along with a serious reconsideration of what "quality of life" really means.
Jeffrey A McNeely is chief scientist of IUCN, the World Conservation Union, based in Switzerland
PETER KENDALL - Biofuels 'will not lead to hunger'
It was really encouraging not only to see how much interest the issue of biofuels aroused but also how supportive many of the responses were.
Fuel of the future? Barley is used to produce ethanol
I very much agree with those - like Nigel Goodman from Macclesfield - who say that 5% biofuel inclusion in our fuel tanks by 2010 is a start, but that we need to be thinking much bigger if we are to make the impact on climate change that is needed.
Maybe the comment from Fred - that we ought to looking at how to create energy from waste - points to one of the areas of greatest potential.
We must always be looking for win-win solutions, and that is what energy from waste offers, particularly in a sector like agriculture. Uncontrolled methane emissions from livestock are a problem, but capturing these emissions to be used as a source of power is a solution.
I would like to see far more research and investment in bio-energy from waste.
Of course, not all of the comments were supportive, and that is bound to be the case in an area as complex as climate change.
Doug Stenson from Doncaster, for example, is worried that bio-energy crops being grown under arable monocultures would be a threat both to biodiversity and human health (not least because of allergic reactions to oilseed rape - which was another concern).
What we need to bear in mind is that we can make sure, through schemes like the UK's Assured Combinable Crops Scheme, that biofuel crops grown in this country are produced in a sustainable manner.
That is much more difficult to guarantee with imported biofuels, and particularly when it comes to palm oil, which may have been grown on cleared rainforest.
I agree absolutely with the many people who warned that in seeking solutions in one aspect of environmental quality, we do not create new problems.
However, there does seem to be a consensus that using biofuels to reduce our dependence on climate-damaging fossil fuels does make sense and can be achieved, at least on a limited scale, without jeopardising our productive capacity for food.
For the sake of the planet, we have to move from meeting our energy needs from the products of ancient sunlight, to using present sunlight converted through photosynthesis into energy and a vast range of other products, by farmers.
The case for biofuels is a strong one, as "Skemps" from Durham remarked: "All we need now is Jamie Oliver to take care of the PR side of things!"
Peter Kendall is the president of the UK's National Farmers' Union (NFU)
GARETH EDWARDS-JONES - Food miles don't go the distance
Writing for the Green Room has been one of the most interesting events in my working year. The responses have been fascinating and I would like to answer a few of the questions directly.
Many people seem to believe that local is best, even though they do not present any evidence for this belief
Anthony, from Oxford, wrote: "If I was a cynic, I'd be wondering if his research grant came from some big food importer, or perhaps an oil company." While R Charlesworth had a similar question: "I, as others have asked, wish to know who is funding the research here as it does seem biased."
The research is funded by the UK research councils under the Rural Economy and Land Use (RELU) theme.
The Economic and Social Science Research Council (ESRC) are taking the administrative lead, but the other research councils contribute funding, too.
Also, I have never worked for an oil company, nor a big food importer, and I have no financial interests in any company or organisation of any sort.
'Absence of proof'
Some people seemed to think that I had forced my opinion on the BBC. This was not the case. The BBC asked me to write an article, to which I initially said "no".
They then used their powers of persuasion to get me to write something anyway, and having read people's comments, this was a decision I immediately regretted.
With hindsight, however, the range of responses spurred me on to do more research in this area.
As Anthony from Oxford goes on to write: "You can't rubbish an idea simply because we don't have all the statistics to back it up. Absence of proof is not proof of absence. Every scientific law starts as a hypothesis."
The energy in cooking food needs to be considered as well
This is exactly right. So my research question is simple: where is the evidence that buying local food is overall a better thing for individuals to engage in than buying food from outside the locality?
As a professional scientist this seems to me to be a perfectly valid question. In order to answer this question I am trying to approach my research in an unbiased manner, and in two years' time when the research is complete, I can communicate our findings in full.
What makes many of the responses so interesting is that many people seem to believe that local is best, even though they do not present any evidence for this belief.
Reader R Charlesworth also made a statement that echoed that of many others: "When I purchase local veg at a local market from a local producer, it IS better than having that same item transported in from overseas. There can be no question about this."
This sort of statement is an anathema to me. As a scientist, I like to question all sorts of things. Then I collect data to help answer the question. I really do not believe that we can progress as a society if everyone forms strong opinions in the absence of evidence, and then holds onto these opinions dogmatically regardless of any new or emerging facts.
'Cahoots with the devil'
It is also clear that not all people share Mr Charlesworth's viewpoint. For example, as part of our work we interviewed a lady from Herefordshire who said that she felt so strongly about the landscape impact of all the polytunnels that had been erected in her county she would buy strawberries from anywhere except Herefordshire.
All in all, the thing that came out most clearly from the responses was how strongly people held beliefs about food, and how quickly they became angry when I questioned those beliefs.
This has been an important lesson for me, and it was a point also noted by someone writing under the name of Foulopinion: "However, the best bit is all those annoyed who write in to complain - when a scientist says something you don't agree with, he is obviously in cahoots with the devil, or rather a big oil company in the words of this 21st Century religion."
Sometimes I wish I was in cahoots with the devil, and then maybe I wouldn't have to spend hot July days writing articles about local food!
Gareth Edwards-Jones is Professor of Agriculture and Land Use at the School of Agricultural and Forest Sciences, University of Wales, Bangor
MATT PRESCOTT - Where have all the leaders gone?
I found the responses to my article calling for stronger political leadership when it came to tackling climate change both encouraging and depressing.
Shoppers make choices based on price not environmental profile
Many people seemed to accept that today's economic markets, as they are currently set up, have done a poor job of including social and environmental costs in their prices.
Many also seemed to agree that braver political leadership was needed in order to force markets to take a fuller account of the long-term consequences.
Just as predictably, a significant number of people seemed to feel that markets should be left to make money as efficiently as possible, unhindered by burdensome regulation, and that businesses should be left to address the problems posed by climate change in their own way.
If you are predisposed to accepting this point of view, perhaps you should also note that no country in the world has a totally free market.
I can accept that markets are relatively efficient at achieving specific goals, once the ground rules for the market have been established, but I don't see why this should mean giving businesses carte blanche and allowing them to do exactly as they please.
Expecting a comparatively small number of profit-focused, and frequently short-termist, shareholders to decide what in is their own interests, and everyone else's, is surely asking for trouble.
Lack of action
Just after my article, the UK Treasury's Sir Nicholas Stern told us that climate change represented the biggest market failure ever, and that the costs of inaction were far greater than the costs associated with urgent and effective action to reduce greenhouse gas emissions.
Given this advice, you might have thought that the world's leaders would be lining up to explain how they were going to stop a large chunk of global economy from disappearing down the plug-hole. Sadly, this has not been the case.
Most of our politicians have remained content to propose the absolute minimum; rather than as much as might be technically feasible, economically justified or possible within their term of office.
In my view, this is because no elected official is prepared to sacrifice their short-term popularity in order to solve long-term problems.
During World War II, Winston Churchill compelled the different branches of the armed forces to co-operate, re-organised the country's industries and spent a huge amount of time studying and co-ordinating almost every sector of society.
Churchill didn't expect the invisible hand of the market to win the war
He did not give speeches in order to make audiences feel warm and fuzzy, nor did he want people to like him. Churchill delivered speeches in order to make his case and get things done.
The public did not always agree with his politics, but the entire nation respected the fact that he had spent years in the political wilderness; warning about the threat posed by Nazi Germany and proposing practical solutions.
Everyone knew that he had their best interests at heart and would not rest until the war was won.
Churchill didn't expect the invisible hand of the market to win the war nor did he expect every individual to work out what their role in winning the war should be. He expected to lead.
Almost all of the most credible scientific and economic evidence indicates that reducing carbon emissions by as much as possible is the right and sensible thing to do.
To paraphrase President JF Kennedy, this means that more of our leaders should ask what they can do for their country, not what it can do for them.
Dr Matt Prescott is an environmental consultant and director of banthebulb.org, an online campaign encouraging greater energy efficiency
RUPERT HOWES - Has the fish supper had its chips?
The positive feedback from many readers is a fantastic acknowledgement of the Marine Stewardship Council's (MSC) work.
Despite this encouragement I still want to respond to a few points to put the MSC's efforts to reverse the decline in fish stocks in the right perspective.
Battered fish stocks may not have had their chips yet
The political reality is that in Europe the Common Fisheries Policy sets the legal framework that determines who can fish where, how much and in what way.
Our fishery certification and eco-labelling programme rewards well-managed and sustainable fisheries according to the MSC standard; it is a voluntary programme that fisheries can choose to participate in.
We developed a market-based approach that offers benefits to all. Retailers, seafood processors and consumers increasingly seek the assurance that their seafood choices do not contribute to overfishing and prefer fish that they can be confident comes from responsible sources.
Our eco-label gives that assurance, encouraging more and more fisheries to embrace sustainable practices. To date, 22 fisheries have been certified, and worldwide there are more than 400 fish and seafood products.
Consumers can find MSC-labelled fish products priced very competitively in mainstream supermarket ranges, which are listed on our website.
A growing number of retailers are stocking sustainably caught fish
The fish used in these products comes from all over the world - Australia, New Zealand, South Africa, South America, the US and Europe.
The carbon footprint this causes is relatively small since frozen fish is mostly transported by ship and not by plane, but there is no doubt that food miles do have a negative effect on the environment.
It would be wrong to assume, however, that buying locally caught fish is always the wiser decision. Local does not necessarily equal sustainable. The examples of many "local" European fisheries that have come under enormous pressure from fishing illustrate this.
Global fish consumption has increased dramatically over the last few years and has resulted in 50% of the world's wild fish stocks being fished to their biological limit, with 25% being overfished.
If stocks are not managed responsibly, we risk losing them forever; not only would this result in a breakdown of the marine eco-system, it could also mean that millions of people would be without a job and more than a billion could lose their primary source of protein.
The MSC urges people to choose fish with its bold blue eco-label to reverse this trend and instead create sustainable, productive fisheries that will meet the needs for future generations and support a flourishing marine environment.
Rupert Howes is the chief executive of the Marine Stewardship Council, the London-based charity that works to promote solutions to the problem of overfishing
The Green Room is a series of opinion pieces on environmental issues running weekly on the BBC News website