Cutting out the old wood, part 3

(… continued from Cutting out the old wood, part 2, posted on 14 Dec 2016).

In its report on the HS2 no net loss (NNL) calculation, Natural England (NE) recommends that, whilst “ancient woodland is considered to be an irreplaceable habitat and hence it is excluded from the Defra offsetting metric”, nevertheless “some compensation factor is needed” in the case where “loss of ancient woodland is unavoidable” (see footnote 1).

Whilst NE concedes that there is a need for its advice on a suitable compensation factor, based on the ratio of the area of compensation habitat to be created to the area of ancient woodland lost, there is some hesitation expressed about making a firm recommendation. This is because, the report explains, “there is little evidential basis to justify any one specific ratio” (see footnote 1).

In its report NE chews over what evidence there is. In a table in its report (see footnote 2), NE compares the biodiversity value of original and created woodland habitats, in terms of “biodiversity units per hectare”. If this comparison is made on the basis of the standard Defra Biodiversity Offsetting Metric values for “metric multipliers” it can only be done for “other woodland”, i.e. woodland that is not classified as ancient, because Defra does not include ancient woodland in its offsetting metric, as it is irreplaceable. So the figures derived from the Defra metric effectively underrate the biodiversity value of the lost habitat. On “worst case assumptions”, which requires assuming that the “difficulty of recreation” is “very high”, NE has calculated that the appropriate compensation ratio is 1:30 by area, whilst cautioning that this assumes that the quality per hectare of original and recreated habitats are equivalent.

Controversially, HS2 Ltd did include ancient woodland in its offsetting metric, and so NE has also made the same area comparison for original and created woodland habitats using the HS2 Ltd metric multipliers appropriate to ancient woodland. If worse case assumptions are made again, the appropriate compensation ratio rises to 1:60 by area. NE cautions, however, that this higher ratio figure assumes “that all ancient woodland is in good condition and very difficult to replace” – the latter is probably a much surer assumption than the former – and that the ratios “have more meaning relatively than absolutely” (see footnote 1). If the difficulty of recreation is only “medium”, then the required compensation ratio reduces to 1:9 by area (see footnote 2).

No doubt wishing to err on the cautious, NE makes the recommendation that “where ancient woodland is to be replaced by new woods, an area based ratio of 30:1 is appropriate” (see footnote 1).

For its part, HS2 Ltd has refused to give a commitment to meet the ancient woodland compensation ratio recommended by NE, gratefully seizing the excuse that “the evidential base is lacking” and claiming that “this part of the [NE] report should be seen as a stimulus for debate” (see footnote 3). The truth of the matter, it would appear, is that HS2 Phase 1 falls far short of the NE recommended compensation ratio: NE calculates that the “overall ratio for ancient woodland losses reported by HS2 Ltd represents 5.25ha of woodland compensation for each hectare of ancient woodland lost; a ratio of 5.25:1 by area” (see footnote 4).

For some time now, the Woodland Trust has been campaigning for a 30:1 compensation ratio for ancient woodland, and defends this proposal as “not something that the Trust has just made up”, but as a figure that “can be derived from the Defra metric” (see footnote 5).

So the stage was set for a bit of a ding-dong when the Woodland Trust appeared before the House of Lords HS2 Phase 1 Select Committee in November 2016 to have its petition against HS2 heard.

(To be continued …)


  1. See paragraph 10.17 in the report Review of the High Speed 2 No Net Loss in Biodiversity Metric, Natural England, November 2016.
  2. See Table 10.1 on page 49 of Review of the High Speed 2 No Net Loss in Biodiversity Metric.
  3. See the first paragraph of the section Ancient Woodland in the HS2 letter of 22ndNovember 2016 addressed to The Woodland Trust.
  4. See paragraph 10.11 of Review of the High Speed 2 No Net Loss in Biodiversity Metric. NE cautions, in footnote 9, that “it is unclear whether compensation used for the calculation is exclusively associated with ancient woodland losses or also relates to other losses resulting from the scheme” and that if “the latter is true, then the reported ratio overestimates the level of actual compensation”.
  5. See paragraph 70 in the Proof of Evidence that Richard Barnes submitted to the Lords HS2 Phase 1 Select Committee on behalf of the Woodland Trust; also displayed on exhibit A692(19).

Acknowledgement: Exhibit A692(19) has been extracted from the bundle of evidence submitted to the Lords HS2 Select Committee by the Woodland Trust. At the time that this blog was first posted the Woodland Trust exhibits were not available on the website of the Lords HS2 Select Committee, and I am indebted to the Trust for making them available to me.



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