t is a very good question and one that is being directly addressed by a number of "Rewilding" projects at present.  As someone who is called upon to manage nature reserves I can say that I am always looking for the least intervention possible to retain the identified site interest. Where possible allowing natural succession to run the show is the preferable option.

So why do we do any site management at all? One obvious reason is that most reserves have visitors and they need to be kept safe, have usable access and something to see without compromising the wildlife interest of the site.

On a site like Blashford Lakes these issues would probably be the main driver of most of the reserve management done by the staff and volunteers. Nature reserves are where people get a chance to engage with wildlife, where education about the natural world can take place and where we can just enjoy the natural world.

Beyond visitor safety and quality of experience the priorities start to get a bit more subjective. Thankfully the days of managing a site for a single species are largely gone, today nature reserves are about habitats and the suites of species that might live within them.

There is no question that fashion has been as much a driver in nature conservation as in most other fields of human activity. Certain species or habitat types being flavour of the month (or perhaps decade) and much else that is truly wonderful getting sidelined.

So how do we decide what to, or if there is a need to do anything? The first thing is consider the data, see what is available, collate all the information we can find and identify the gaps in knowledge that need filling.

At Blashford Lakes nature reserve we knew the lakes were of international importance for wildfowl, so management for these species was going to be important. The lakes are a recently created habitat and are changing so we also need to keep an eye on how they are developing, where changes are outside practical management control  this needs to be recognised so that we achieve the most sustainable future of greatest benefit of wildlife.

Since we have been running the reserve we have discovered a number of notable species including several new to the county and this information informs management, either indicating that something should be done, or not done.

Most nature reserves are not in a climax habitat state, that is if they are left alone they will not stay the same, this is called habitat succession. This may not matter, except that most reserves were established because they had interest for wildlife and change implies potential loss of this interest, even if it might also include the acquiring of new interest.

Importantly nature reserves exist in a context, they are rarely large enough to support viable populations of many species, so the habitat of the wider area is also a vital consideration.

One undesignated (i.e. not SSSI) part of Blashford Lakes is the lichen heath, it turns out that this probably home to more rare species than any other part of the site. It will  slowly turn into secondary birch woodland without intervention, so in this case there is probably a good case for trying to halt this successions and "reboot" the area to allow continuation of this habitat beyond its natural lifespan.

Fishlake Meadows

Our new reserve at Fishlake Meadows is a great example of how nature can reclaim an abandoned area. A natural looking wetland developed rapidly once the pumps that sustained conventional agriculture were turned off.

The reserve is now one of a string of important wetlands along the Test Valley, from the brackish transition marshes of the Lower Test through the standing waters of Testwood Lakes and on up through the Broadlands Estate, the string continues north to Mottisfont and beyond and all linked by the River Test itself.

It quickly developed into an area of pools with reedbeds and tall fen, plants that could colonise freely from the species rich habitats close by. The existing trees mostly died as their roots became waterlogged, but new trees came in, mainly willows, well adapted to wet conditions.

The resulting mosaic of habitats attracted many species, including a number of scarcer ones. Surveys at this time showed just how diverse the site had quickly become, its potential for wildlife was clear, the task was how to secure the site as a long term haven.

Now that Fishlake Meadows is a reserve new surveys are being conducted. What was immediately clear was that the fen plant communities were more restricted and less diverse than they had been a few years before. This appeared to be because they vegetation was taller and dominated by fewer larger species.

It was also clear that the willow scrub has turned into woodland in many areas shading out the vegetation underneath and was continuing to expand. Closed canopy willow woodland will develop quickly in reed swamps and fens if the water is not too deep and although good for some invertebrate species it is generally less diverse than the earlier successional habitats it replaces.

It is also not a particularly rare habitat and can be found widely along the less managed parts of many of our river valleys. Fen grasslands are much rarer and as are many of the species that depend upon them.

It is reasonable to ask "Why intervene to try and keep short-lived habitats?" We could just step back and watch. It is also interesting to ask "How come these species that depend upon early successional stages are here at all?".

If we try to look back in time much of the country would have been covered in woodland, trees are the natural climax vegetation type for this part of the world. This cover would not have been continuous though, the landscape would have included large herbivores, such as wild cattle, wild boar and other species that would have changed the plant communities like beaver.

These along with natural floodplains would have resulted in areas where trees were fewer, indeed beaver dams may well have had the same effect on trees in valleys that turning off the pumps had at Fishlake.

These lost species would have prevented ares from achieving their potential climax vegetation type resulting in scrub, glades and perhaps extensive grasslands in suitable locations. Work at the Knepp Estate in Sussex is showing how having a range of large herbivores, in this case domestic animals that mimic the activity of wild species, produces a varied mosaic of habitats, very like that aimed or by most nature reserve managers. They maintain areas of early successional habitat without the need for constant intervention.

Many other valued early stage habitats are entirely man made, hayfields would be an example, even though the species could have survived in grazed grasslands they would not have achieved the densities experienced in managed hayfields. So sometimes we are managing to maintain historic land practices that happen to be good for wildlife, although they are not natural.

So we undertake management for people, in an attempt to mimic the likely impacts of  larger habitat changing species which we have now lost from our environment or to maintain historic human activities which have produced habitats which we deem to be of interest.

The less work we have to physically do ourselves to achieve this the more land we can manage for wildlife. Low density grazing by hardy cattle breeds seems to be a fair substitute for the impact of wild herbivores, which is why the Trust has a herd of native breed cattle. If we can get the regime right the fen habitats at Fishlake should require very little intervention to be maintained, grazing will open up ares of shorter vegetation and reduce scrub invasion.

Together with other areas where succession will continue this will hopefully maintain a complex and diverse habitat for many years to come.

How wild should we go? As wild as we can, if we allow space for nature it will thrive, but space is everywhere, if we confine nature to nature reserves many species will not survive. We need to remember that to survive a species needs continuity of the resources needed for survival.

Maintaining habitat diversity is key to maintaining species diversity and the greatest range of resource continuities. Extinction is a once in a lifetime event best avoided or at least put off for as long as possible.

If we can start to set aside really large areas we might actually be able to step back entirely and let things go properly wild, but perhaps we are not yet ready for wild cattle, lynx, wolves and all the rest.

We may like our wildlife, but not be ready for it to  be properly wild just yet. In the meantime we will have to manage habitats and continue in our roles as proxy aurochs and substitute beavers.