At the end of June I went for a walk over Conic Hill, starting from Milton of Buchanan and then back along the main road from Balmaha. The first part of the route, which I have followed several times before, takes the West Highland Way through the western edge of Garadhban forest, owned by Scottish Ministers and managed by Forest and Land Scotland (FLS).

It was my first visit since FLS consulted on a draft Land Management Plan (LMP) for Garadhban forest last year (see here).  FLS’ intention is to manage most of the forest as a mixture of conifers and broadleaves, using Low Intervention Silvicultural Systems (LISS) and natural regeneration rather than planting, but reserving the western compartments of the forest for native woodland.  The north west corner of the forest, known as Garadh Ban wood, was planted with native trees around 15 years ago:

Since I first started looking at the native woodland on the western edge of Garadhban, the number of native Sitka appear to have steadily increased.  As they grow faster, many of the Sitka are now significantly taller than the native trees and threaten to out-compete them

While Scots Pine is the mostly widely distributed conifer on earth, the absence of other large conifers from Scotland made our native woodland unique. Scotland’s native woodland lacks the dark closed canopy conifer forests found elsewhere in the northern hemisphere.  Where Sitka is invading native woodland, however, as at Garadh Ban wood, it threatens to change that character entirely and could eventually out-compete and kill off most of the native trees.

That eventuality, the likelihood of which appears to be increasing at Garadhban year by year, is clearly contrary to the intentions of LMP which depicts the whole area I walked through as native woodland.  There is no mention of this issue, let along what FLS plans to do about it, in the draft LMP which is still to be approved by Scottish Forestry although there is reference to an ‘ingress of Sitka’ in a broadleaved area on the eastern side of Garadhban that is due to be thinned (coupe 61601 on the thinning map).

Sitka don’t produce seed until they are about 20-25 years old and the problem on the western edges of Garadhban appears to have been made worse by FLS’ decision to retain a strip of mature Sitka (light blue on top map) along the southern part of the native woodland to provide more structural diversity to the forest.  Each time these trees seed, the native woodland to the west faces an invasion of Sitka.

 

While it is easy enough to remove Sitka seedlings from open moorland (see here), when Sitka invades densely planted native woodland it’s another matter: the young Sitka, among all the other vegetation growth are much harder to detect and then, as the native woodland grows, extracting them becomes more and more difficult.  Leave it to long, as FLS have done at Garadhban, and the landowner either faces considerable expense or losing the native woodland they had intended to create.

 

The failure of FLS’ draft LMP to describe how Sitka (and other non-native conifers such as Western Hemlock) are invading the area reserved for native woodland at Garadhban let alone what they plan to do about this suggests it has been a desk top exercise. The approach to Sitka contrasts with its proposals to remove the remaining 14.9 ha of larch in the forest (3% of the total) ‘in an effort to slow the spread of Phytopthera Ramorum’.  Why is FLS doing this, even though ‘there are no active plant health concerns’ in the LMP area, and not making any effort to slow the spread of Sitka?

Part of the explanation is that Sitka, despite being non-native and highly invasive, is not classified by the Scottish Government as an Invasive Non-native Species.  This has allowed foresters to absolve themselves of responsibility for what is happening on the ground (see here) and explains this statement from FLS’ LMP:

A.6.10 Invasive Species
There are no known areas of non-native invasive species in the woodland block; however, there is a significant amount of Rhododendron Ponticum ~800m south of the block boundary which has the potential to seed into the block

Meantime Phytopthera Ramorum, an invasive disease which spreads through the air, is classed as a threat to plant health even though it is clear now that removal of larch won’t stop its spread.

FLS’s draft LMP fails also to say anything about the risks that other landowners face from ‘Sitka ingress’.  This is likely to become a major problem for the Montrose estate because, as the plan reveals:

‘A.6.6 Adjacent Land Use
To the north and west, Garadhban borders land of Montrose Estate which has recently excluded grazing from the area with a view to potential woodland establishment’.

Reduce grazing levels and Sitka, one of the least palatable of tree species found in the British Isles, spreads.

 

 

 

Sitka have been in the process of colonising Conic Hill, part of which is a Site of Special Scientific Interest, for over a decade.  Its special flora, some of which is associated with the Serpentite conglomerate from the Highland boundary fault, were thought to being damaged by overgrazing but the reduction in sheep numbers appears to have opened the door to a new threat, Sitka.

 

FLS’ LMP recognises the special landscape character of east Loch Lomond where it is attempting to enable the oakwoods, which were originally planted, to recover from being over-planted and surrounded by conifers and to develop into a more natural Atlantic rain forest.  It claims, however that as Garadhban lies:

‘3km from the loch shore at the boundary’s nearest point and far below the closest ridgeline of Conic Hill – forestry in the LMP area is unlikely to negatively impact the special landscape qualities of the national park.’

The Sitka on Conic Hill could owe their origins FLS’ plantations at Balmaha, the Garadhban Forest or the Loch Ard Forest to the north-east, other smaller plantations locally or a mixture of those nearby sources.  That uncertainty has allowed FLS to avoid taking any responsibility in its LMP for the Sitka which is spreading out from its large landholdings into east Loch Lomond.

Discussion

The ostensible policy position of the Scottish Government and the regulator, Scottish Forestry, is they wish to promote more native woodland.  Hence the forestry grants for planting native trees and hence the requirements that commercial conifer plantations, when first planted and when re-stocked, include a proportion of native trees.   There is no point, however, in FLS or any other forester planting new native woodland or mixed forests – as at Garadhban – if that woodland is then overrun by Sitka and ceases to be native or mixed woodland.  The invasion of Sitka at Garadhban (and other native woodland schemes) therefore represents a massive policy failure.

Jim Knight, author of a Forest for the Future (see here), who commented on my post on the Sitka invasion of Glen Falloch (see here), believes it is too late to stop its spread and we should adopt a different model of mixed forests, with natural regeneration replacing planting and the trees then managed differently.

Driven by the impact of wind-throw, which has in the past regularly toppled uniform single species blocks of conifers, FLS appears halfway to that model for Garadhban.  Its LMP shows no less than 17 different combinations of species for different blocks within the forest.  For example: Sitka spruce and Scots Pine; native mixed broadleaves with Sitka spruce; Norway spruce with Douglas fir; other broadleaves with Douglas fir.

The challenge is that unless FLS selectively fells the faster growing conifers, Sitka spruce, Norway spruce and Douglas fir, most of the blocks will become monocultures again.  While the LMP does contain proposals for selective thinning, these appear driven more by the need to reduce windthrow rather than a commitment to the model of continuous cover forestry that Jim advocates or is practised on the continent.

While continuous cover forestry or LISS, comprising a mix of native and non-native species, would represent a significant improvement on plantation forestry, it still leaves the question of what to do with invasive Sitka?  Where should they be accepted as a component part of new woodland and where not?  As a starting point, we not only need to protect the integrity of the Caledonian Pinewood remnants and other special areas of native woodland against Sitka and other non-native species, we also need to protect peatland.

To deliver this, we need to develop and map Sitka free zones, as with the buffer zones Scottish Forestry (SF) has drawn  around the 84 sites on the Caledonian Pinewood Inventory.  SF should be developing similar policy requirements for all planted native woodland, otherwise there is no point in it continuing to pay to plant it or requiring others to do so.

The Scottish Government and SF also need to develop mechanisms to make the forestry industry responsible for preventing the ingress of Sitka into all Sitka free zones and removing them where ingress or invasion occurs.  That would not be that expensive if the problem was dealt with promptly.  A single person with a chainsaw could probably cut down most of the invasive Sitka on Conic Hill in a day. Allow Sitka to develop among native woodland, however, or their seed rain to get established on moorland and its another matter.

Sitka is the dominant tree in the Loch Lomond and Trossachs National Park.  The National Park Authority (LLTNPA) could be playing a key role in developing Sitka free zones – how about all land above 500m in addition to those previously suggested (see here)? – and bringing landowners together to address the problem before its becomes too great. Another sign of the LLTNPA’s failure as a National Park is it appears to have no policy on Sitka: it is not mentioned once in the current National Park Partnership Plan 2024-29 which sets the framework for all it does; its Trees and Woodland Strategy 2019-39 has plenty on clearing invasive rhododendron but nothing on Sitka; and there is no mention of Sitka in its vision for Future Nature (see here).

Unfortunately, the senior management and the board of the LLTNPA are completely blinkered and do what they are told by civil servants rather than think for themselves. Imagine what they could have achieved for nature if, instead of employing rangers to police the camping byelaws, which they are proposing to renew just now and describe as pioneering (see here), they had employed them to remove Sitka instead?  That might have actually made a difference for nature,

[I intend to follow up this post with another on the impact of invasive Sitka on attempts to restore native woodland along the shore of east Loch Lomond part of which is already supposed to be a Sitka free zone].