The National Trust wants to preserve more of the Capital's rich past, but first it must face the future

Everyone in Edinburgh knows how vital heritage is to the economy. Whether it's the Castle, the country's number one tourist attraction, or living history events for kids at the Georgian House in Charlotte Square or at the 17th-century tenement Gladstone's Land in the High Street, the past fascinates and enriches us.

The National Trust for Scotland is the charity entrusted with conserving some of our most iconic landscapes, buildings and collections. The responsibilities are daunting: 130 nationally important sites, 1500 individual buildings, 200,000 acres of countryside, 46 Munro mountains, 248 miles of coastline, 16 islands, the habitats of a million breeding seabirds and the conservation of 100,000 objects, including works of fine art and the everyday tools of lives once lived.

Our job is to explain what these mean within the ongoing story of Scotland and ensure their survival for future generations.

That's a long list and a big ask for a charity. These responsibilities would challenge even a government department and it has been difficult for the Trust to say "no" in the past when presented with yet another historic building that must be saved.

Matters came to a head two years ago when it became clear that we were spending far more on the upkeep of our properties than we were taking in from membership subscriptions and other income.

The result was an independent review with a series of recommendations that included streamlining our governance.

We now have a new board of trustees in place. We are seeing improvements in our financial position but our long-term survival, and our mission, depends on setting out a strategy that focuses us on our conservation objectives. We must become financially sustainable and not bleed resources on anything that doesn't fit our core purpose.

Two years ago it seemed as if we might have to close ten per cent of our main properties. We managed to avoid that with the help of local communities and our ever-reliable volunteers, as well as improved finances. Our goal in the next five years is to consolidate our position and maintain all of our nationally important properties.

But, we want to go further than this. Our strategy will include a review of our entire property portfolio to help us prioritise future investment.

Most of this investment needs to be self-generated - although we do receive generous government support for specific projects, we don't generally receive money from the taxpayer. That means we have to develop more income streams from which we can re-invest the proceeds in conservation of our heritage.

What we do to achieve more income will very much depend on each property and will be entirely sympathetic to its setting and history: options may include business partnerships with complementary organisations, such as at Hill of Tarvit near St Andrews, where a catering company is supporting our initiative to attract corporate events, or the sub-letting of peripheral buildings on larger estates for holiday homes and tenancies.

Whatever the case, we will be investing in pioneering, exciting and challenging ways of presenting the history and context of our properties.

We want to help people connect with their past and their heritage in ways that respect tradition but embrace new techniques. With new priorities, the flipside is that there are some things we have to stop doing - with only 400 permanent and 700 seasonal staff across the country we cannot do everything, even in five years.

Unfortunately, this means tough decisions - such as have been made about Suntrap Garden and a community garden in Duddingston: much as we would like to carry on supporting these sites, they do not have any heritage value and in all conscience cannot be said to meet our core purpose.

Nevertheless, our ultimate ambition is that we will be once again be ready to take on more properties that are of true national importance. It is too early to say where or what, or even if we will be ready to do this in five years, but we are clear that there is much we could add to our portfolio to tell the story of Scotland, especially over the last 100 years, and this may well include additional sites in Edinburgh.

It has been suggested that we should be looking at examples like the amazing Art Deco Odeon cinema in Clerk Street and sites that can reflect the Scottish Enlightenment as led in this city. We would love to do this, but first we need time to make the necessary changes described.

We will finalise our new strategy in September. It will represent a new chapter for the Trust and its place in telling the long, long story of Edinburgh and the rest of Scotland.

• Kate Mavor is chief executive of the National Trust for Scotland