23/03/2015 13:35 GMT | Updated 23/05/2015 06:59 BST

I Hope Octavia Hill Would Be Proud of Her National Trust

"Standing on the shoulder of giants", to use Newton's famous image, can be a wobbly business. More precisely in my case, standing on the shoulder of a giantess. So I was distinctly reassured today to read this quote from Octavia Hill, one of the founders of the National Trust, "When I am gone, I hope my friends will not try to carry out any special system or to follow blindly in the track which I have trodden. New circumstances require various efforts...and it is the spirit, not the dead form, that should be perpetuated".

Octavia was speaking at the unveiling in 1898 of her portrait by John Singer Sargent. If she is looking down on us now, I hope she approves of what "her" Trust is up to. We are about to launch a new ten-year strategy, answering the question, "What does the nation need from the National Trust in the 21st Century?" As I've learned more about the history of the Trust in my two years in this job, what I think is amazing about it is its capacity for reinvention - in facing up to the challenges of the day and not (and here may be an irony) living in the past.

When Octavia and her co-conspirators Sir Robert Hunter and Canon Rawnsley were planning the Trust, the problem they thought they were solving was access to the open air for the urban masses. Octavia had been fighting the good fight for years to protect green spaces in London, like Parliament Hill Fields and Hampstead Heath. This was a natural complement to her decades of work, initially alongside John Ruskin, to provide decent housing for poor families and give them active support in turning round their lives (she was definitely a believer in Samuel Smiles rather than municipal socialism).

By the mid-20th century, the challenge to our charitable purpose "to promote the preservation of places of historic interest and natural beauty...for the benefit of the nation" came not from the loss of open spaces but from the wholesale destruction of the English country house. Between the wars, economic depression, high estate duties and the loss of many sons and heirs in the First War, meant that this unique expression of English culture was under threat of being lost. A sweet deal with the Treasury (under which houses could be transferred to us in lieu of tax) brought to us and the nation many of the great houses (Hardwick, Kedleston, Knole), for which we are probably most famous today. But I don't believe that Octavia and her colleagues would ever have imagined that we would have been in the large-scale house conservation and visitor business we are in today.

Fast forward to 2015, and what do we think is the biggest challenge the nation faces, in which the National Trust we can play a part? It's not saving great houses any more, though we need to make sure that people carry on enjoying them and feel that the past they represent is still relevant to their lives today. No, the threat is to the health and beauty of our countryside. There are heart-breaking statistics for the decline in wildlife species that people really love and we once thought common - skylarks, hedgehogs, song thrushes, large blue butterflies, starlings and house-sparrows. 60% of our wildlife species are in decline.

Over the last 40 years, intensive farming and the misconceived subsidy systems that drove it, have been responsible for much of this loss. Now and for the future climate change may well be the biggest threat, with extreme weather and higher average temperatures damaging habitats and driving species to look for asylum elsewhere. Professor John Lawton in his "Making Space for Nature" report in 2010 said that the destruction of our most precious wildlife sites was as though, of our 27 great cathedrals, "twelve had been partly demolished, nine substantially demolished, and three completely obliterated; only three would remain in good condition."

So this is where we will be focussing our efforts and our resources over the next ten years: sorting out the state of our own 250,000 hectare backyard (or rather, the nation's backyard), in partnership with our farm tenants, and working with other partners like RSPB, The Woodland Trust and the Wildlife Trusts, to see whether we can create the "bigger, better, more joined up" landscape scale habitats that John Lawton said we needed. Oh, and to deal with cause not symptoms, we'll be pressing on with our ambitious plans to get 50% of the energy we need from renewable sources like hydro and bio-mass, sourced from our land.

Sound OK, Octavia?