From yield class to BioClass

Coillte has designated 90,000ha of its estate as biodiverse habitat, as outlined at the company’s Biodiversity Seminar at the Science Gallery in Trinity College last week (11 September). This means that 20% of Coillte lands are managed according to ecological objectives. It represents a sizeable portion of the overall company estate, which covers an area larger than counties Clare and Carlow combined. This ecological designation ensures that 222,000 acres – greater than Co Carlow – are treated as a major national biodiversity resource. The company has developed a biodiverse or BioClass system of grading these areas rather than the traditional forest production related yield class (YC) system, which provides forest data on annual timber yield in cubic metres (m3) by tree species, age and area.

BioClass provides a range of information on tree (forest, woodland and scrub) and non-tree (bog and heath) habitats. The estate is divided almost in half between forest and open habitats, with forest habitat comprising native forest (11%), broadleaves (7%), mixed forest (8%), conifers (15%) and scrub (7%) while open habitats comprise bog (28%), heath (23%) and other habitat (1%).

There are echoes here with the ancient Brehon law dealing with trees and woodlands. The old Irish tree list from Bretha Comaithchesa, created a four-tier hierarchical grading system for trees and plants with Class 1 being the highest including trees such as oak, ash and pine (now Scots pine).

The BioClass also features four grades – habitat rather than tree species – with BioClass 1 being of highest biodiversity value. In all, 2,300 Coillte sites are mapped and ranked as follows:

Coillte ecologist, Dr Aileen O’Sullivan, who led the design of the BioClass system, said the company’s estate provides habitats for many plants and animals, and represents a major biodiversity resource.

“We developed BioClass because we needed a tool that enables us to flag important sites, prioritise resources and integrate biodiversity into forest management planning,” she said in her presentation to the seminar. “The tool will enable Coillte to ensure its biodiversity areas are properly managed and resourced.”

Dr O’Sullivan, and her team – with company funding of €750,000 – developed a set of habitat codes which “describe the site type in terms that are closely aligned with Coillte’s forest inventory”. In addition, codes were developed to summarise a high level of management options for each site.

For example, habitats currently ranked as BioClass 4 which have moderate value “have the potential to develop into habitats of high ecological value”.

The rationale behind this new BioClass system “marks a new phase for Coillte and biodiversity in Ireland” , according to Fergal Leamy, Coillte chief executive.

“Over the past 29 years, Coillte has been the custodian of some of the most diverse and important biodiversity sites in Ireland, and we take this responsibility very seriously,” he said.

“Coillte has invested significantly into restoring and managing Ireland’s key biodiversity habitats, but we believe more needs to be done to secure the future of these habitats’ longevity.”

In addition to Dr O’Sullivan’s presentation, science and wildlife TV presenter, Liz Bonnin and botany professor Jane Stout of Trinity College Dublin and chair of the Irish Forum on Natural Capital, also spoke. Liz Bonnin highlighted the importance of the commercial sector, investing in natural assets. Commending the Coillte initiative she said:

“Each and every one of us can play a role through changing our habits and behaviours, but corporations, and policy-makers must step up and lead the way.”

Jane Stout outlined the importance of biodiversity and non-wood aspects of the forest.

“Forest systems don’t just provide timber and other products, but they sequester carbon, release oxygen, help stabilise soils, and provide a home for other living organisms,” she said.

Biodiversity in Irish forests

The allocation of one-fifth of the Coillte estate as biodiverse habitat prompts the question about the ecological potential of the total forest estate in Ireland – private and Coillte. Data in the latest National Forestry Inventory (NFI) suggests that the biodiversity resource includes a high prevalence of non-tree plant species and lichens in the forest estate. “Nearly half (49.3%) of the forest area has vegetation coverage of greater than 90%,” the NFI claims. “There are significant proportions of open areas and areas with natural regeneration present, the latter particularly so in the older private forest estate.

Plant diversity

Plant diversity is an important indicator in monitoring sustainable forest management (SFM) as “the structure and range of the vegetation present will also be indicative of the insect diversity,” according to the NFI. “Nearly half (49.3%) of the forest area has vegetation coverage of greater than 90%, excluding the tree species present. Older private woodlands (established before grant aid in the early 1980s) have greatest diversity with “80% of the area having nearly a vegetation coverage of greater than 75%”.

“All stocked forest areas have up to five different plant species present and over 80.5% have between six and 21+ plants species present,” the inventory claims.

“Large woody material contains very significant stores of carbon and energy and is the foundation of an important forest food web. This large material usually decays more slowly and therefore provides a steady input of energy and longer-lasting structures for the ecosystem.”

The inventory stresses the importance of deadwood which provides habitat for plants, animals and insects and a source of nutrients for soil amelioration. There are 10.4 million m3 of deadwood in the forest estate comprising trees decaying on the forest floor, standing dead trees, stumps and biomass litter. It would be an interesting exercise in the next national inventory to assess the biodiversity areas of the total forest estate in terms of its ecological value based on the Coillte BioClass template.