YOU only had to be out and about on Westcountry roads this bank holiday to know why it was necessary for this newspaper to commission a series called Contested Landscape. England is one of the most heavily populated countries in the world and the figures are growing fast – the sheer pressure of numbers is bound to impact upon the natural environment.

Despite what tourism bosses have been saying this week about a potential downturn in visitor numbers, the region's highways were clogged – certainly on Sunday, when the great urban masses were heading West for a day out somewhere pleasant in the cool spring sunshine.

Which is all well and good – their spending must have been excellent news for thousands of local businesses in the countryside. The big migration couldn't really have had too great a detrimental effect on the landscape either – after all the visitors were, for the most part, here one day and gone the next.

But the Contested Landscape is about more than just bank holiday weekends – it is about the endless, unerring pressure that mankind puts upon the natural environment, and about what we can do to alleviate that strain.

That alleviation – that easing and salving – is crucial, not only because the countryside looks nice and we all like to enjoy its scenery and fresh air, but because it contains ingredients that are vital to our overall wellbeing. Its ability to produce fabulous first-class healthy food is of course just one of the countryside's assets – but there's far more, as the series has discovered.

We hope we've been able to give readers something of an overview of how the landscape is being regarded – how it is being cared for and, indeed, harmed – here in the South West. Because you could argue the state of the landscape is more important to this rural peninsula than any other single UK region.

The Westcountry is one of the nation's premier holiday locations – people come here because they like the look of the place – so it is imperative we keep those good looks intact.

But, as I say, the visual amenity is only half the story. Travel around the region and you will find contested elements concerning the landscape in just about every corner. So far this 18-part series has dealt with many of the issues, but by no means all – which is why we intend bringing back the Contested Landscape articles in the autumn.

In this round-up, though, we look at some of the main issues that underlie both the threat to our natural environment, and the steps that are being taken to counteract the negative impact mankind is having upon that amorphous and emotive thing called the countryside.

"Oh no – you're not going to write an entire series about a bunch of sandal-wearing ecologists spending vast amounts of public money on saving some wretched frog, toad or butterfly!" So exploded one old cynic I know when he first heard about this newspaper exploration.

And blow me down if I didn't find myself standing in a boggy bit of North Devon gazing at a butterfly egg smaller than a match-head, listening to an expert wax lyrical about the millions being spent to help to save the rare and elusive brown hairstreak.

That old cynic of my acquaintance would have burst an angry blood vessel on the spot. But even he saw sense in the scheme after he'd read the WMN article in which the entire story of culm grasslands was told. Those millions turn out to be well spent.

Wherever you find one healthy rare butterfly, you'll probably discover a whole good news story waiting to be told. In this case it was to do with the fact that intensive agricultural practices of the past half century haven't exactly helped when it comes to the supply of good fresh drinking water.

We'd been up in North Devon researching an article about the threatened culm grasslands and Peter Burgess, project manager for Devon Wildlife Trust's Working Wetland scheme, was showing us this rare type of natural environment and the even rarer butterfly egg.

"One of the culm grassland's most important roles is in helping to ensure a clean water supply," explained Peter. "They act as filters and buffers against pollutants arising from modern agricultural practice."

For decades the culm grasslands were generally regarded as being useless to man and beast – they were only of any worth if they were drained and generally had seven bells knocked out of them in a bid to "improve" the land.

But now the raw, primeval, untouched culm grasslands the have taken on a big new value.

It turns out these grassy, sedge-filled wastelands provide a cost effective way of keeping our drinking water supplies clean. Until now the water industry has concentrated on what it calls "end-of-pipe" cleaning – in other words various filtration techniques are carried out just before the water reaches household taps.

Now there is a move to look at what is going into the water at source – up in the hills where it rains. And rain is one thing it does a lot on culm grasslands. The trouble is, it washes away many of the artificial nutrients farmers use to make their fields more profitable – effectively making them less profitable.

"It's very expensive for farmers to lose nutrients in the first place, before we get to cleaning up the water," says South West Water's environment manager, Martin Ross. "We all want to keep fertiliser where it belongs, in the fields not the water, which is one of the reasons we are supporting the Working Wetlands project.

"It costs us 20 per cent more to treat dirty water than clean water on a day to day basis – and if it [nutrient pollution] gets really endemic, it causes the blue-green algal blooms that we've seen at Roadford Lake. That can become even more expensive for us to clear."

Roadford Lake is just south of the main area of culm grasslands – if their natural filtering systems can clean up the water flowing into the reservoir, then South West Water will save money which, ultimately, means the consumer will too.

Peter Burgess had something else to say about the water flowing from culm land: "Alleviation of the peaks and troughs of river flows is very important – culm acts as a sponge soaking up water in periods of high rainfall and slowly releasing it during periods of drought."

So there's a win-win-win situation if ever there was one – we are saving on the massive costs of making drinking water clean and of building expensive flood prevention schemes – and as a bonus we get an extensive and healthy natural landscape, which happens to contain a rare butterfly. Suddenly, the cost of giving that rare brown hairstreak butterfly a home seems cheap. It thrives on culm grasslands and is part of the visual evidence that such habitats are in a good state of health.

The "rare butterfly returns to its native Devon heath" is an easy story to tell. But the greater story – the tale about algal blooms in reservoirs, industrial scale water cleaning plants and expensive flood prevention schemes – is a more difficult narrative to put across.

That's because it contains elements that environmentalists call "externalities". You'll hear this phrase a lot if you dig deeper into our contested landscapes. It basically relates to the hidden costs of mankind's many activities.

For example, our reliance on burning fossil fuels has many unseen and expensive consequences. Just because we don't pay directly for them, doesn't mean they don't exist. Someone somewhere will be paying – sometimes the taxpayer, sometimes people in other countries.

To take a specific case, you could argue the cost of going to war in Iraq to secure oil was not reflected in what we pay at the petrol pumps. But it was most certainly accounted for in our taxes.

We might not see it, but by externalising such costs, our reliance on burning of fossil fuels is being massively subsidised. Let's take another example: the source of recent swine-flu scare is generally believed to have been triggered somewhere in the bowels of gargantuan over-industrialised "farms" designed to produce pig meat at a pittance.

There's an irony here, and it is full of "externalities". Many of the Westcountry's traditional landscapes look the way they do because animals have been farmed on them for centuries and the grazing beasts have shaped the countryside we see and enjoy.

But now, as we've heard in this series, the Westcountry hill farmers who traditionally produce fine quality meats are being priced out of the market. The landscape suffers, but the consumer says: "It's all very well having nice animals on nice farms, but that meat is always more expensive and we will only buy the cheapest."

Throw in the financial cost of a worldwide flu-pandemic (in monetary terms alone – forgetting the deaths and misery) and suddenly that cheap meat seems very expensive indeed.

You could go on and on about industrialised farming techniques and the harm they do to the planet's landscapes, let alone the Westcountry's.

You could count the cost of chopping down South American rainforest to create land in which to grow cheap soya, which in turn is fed to animals to create cheap meat. Which suddenly doesn't seem so cheap when you throw in the almost unimaginable costs of the resultant climate change.

But now the world is beginning to count such external costs. The idea that because nature is free you can exploit it is being consigned to the history books.

It was only a fortnight ago that Dame Fiona Reynolds, director general of the National Trust, was telling members of the Exmoor Society that moorland landscapes – once reviled as useless barren wastes – are now being regarded as vital to the country's future.

She claimed the nation needed to rethink its entire approach to using the landscape as a resource: "Climate change has given us whole new set of things to think about. We've been looking at land as far as the produce that we get from it – now we are turning that around and looking at how land can be used as a resource in itself – how it is being looked after and how will be looked after in the future."

Dame Fiona said peat soils found in places like Exmoor played an important role in containing potentially damaging carbons. And she pointed out just how disastrous in carbon capture and landscape terms it would have been if the length and breadth of Exmoor had been put to the plough – a subject highlighted at the beginning of the Contested Landscape series.

"Land is one resource upon which the whole of human life is completely dependent and yet we don't think about it enough in terms of protection," said Dame Fiona, mentioning not only carbon capture but the all-important clean water that places like moorlands hold and supply.

And as our population continues to rise, we need more of nature's gifts like clean water, rather than less. England's population density is more than treble the European average of 117 people per square kilometre – indeed, England is one of the most densely populated countries in the world.

Many Westcountry landscapes haven't changed much for centuries – some, like the high moors, haven't changed at all – and yet the nation's human landscape has grown out of all proportion.

In 1600 there were just four million people living in this green and pleasant land. A century later it was up a million – by 1801 there were eight million – and just 50 years after that the number had risen to a rather startling 20 million. In just 50 more years, that number had doubled. Now we're at 61 million.

No wonder natural landscapes are under pressure. They have been for centuries, and they became even more threatened when mankind invented such things as the internal combustion engine.

Now it's time to be inventive again. We must find new ways of looking after the thing that looks after us.

The subtitle of this series is: What Is the Countryside For? We are just beginning to understand that it's not only there to provide food and look pretty – its precious ecosystems are actually very good at keeping the planet, and us, healthy.

In short, the landscape shouldn't be contested at all – our countryside ought to be regarded as sacrosanct.