We have had a bumpy relationship with trees. Our landscapes were largely treeless at the beginning of the 20th century, with just 1 per cent of Ireland’s land covered by forest.
The native forests that used to cloak more than 80 per cent of the land were gradually removed, from the Stone Age onwards, for timber and agricultural land. Now just tiny pockets of ancient forests remain.
Forests have increased from 1 per cent to over 11 per cent over the past 120 years, with most of the increase due to plantations of non-native conifer species. One single conifer species from the west coast of North America, Sitka Spruce, occupies 45 per cent of Ireland’s forest area.
Our current forest landscapes are like mosaics with a single colour predominating. While Sitka Spruce is a very productive timber tree that also sequesters and stores carbon, it can be negative for native biodiversity if planted in monocultures and clear-cut without appropriate protection of watercourses from sediments eroded from the newly uncovered land. Poorly sited and badly managed forests can be damaging to biodiversity.
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Forests make many different contributions to our economy, health and wellbeing, including wood, water filtration, flood mitigation, habitats for plants and animals, climate regulation and psychological benefits.
These benefits can be provided by different kinds of forests in different areas, the “mosaic” approach, or from a single forest, the “multifunctional” approach. For example, forests close to urban areas are likely to be more heavily visited by people, providing many recreational benefits, whereas forests in the uplands provide water holding capacity that can improve water quality and reduce flooding downstream.
Well-managed forests on the right kinds of soil sequester and store carbon, pulling damaging carbon dioxide from the atmosphere. If trees are harvested and the wood is used in long-lived products such as building materials and furniture that carbon can be stored for decades to centuries. Other trees can then be replanted or regenerate naturally on the same land sequestering more carbon, and so on.
Given the tempo of forest planting in Ireland we are now approaching a “carbon cliff” where from 2025 to 2030 our forests are projected to be a source of greenhouse gas (GHG) emissions rather than a sink.
There are a range of reasons for this reversal, more forests are reaching maturity and being harvested than are being planted, many forests planted in the 1980s were planted on peat soils which, when drained, emit GHGs and older trees grow more slowly than younger trees.
There are many solutions to our forest conundrums. Ireland’s Forest Strategy promotes multifunctional forests and more diverse forest mosaics. More broadleaf trees will be planted and open non-forest ecosystems will be maintained within the forest footprint.
Continuous cover forestry, or close to nature forest management, maintains a forest canopy while small numbers of trees are harvested regularly rather than the entire forest being clear-felled.
This type of forest management protects the soil, maintains carbon within the ecosystem and allows for the best timber to be extracted and replaced through planting or natural regeneration. A more complex forest structure arises, with trees of many sizes and several different species can be included. Structural diversity is good for nature.
We need to plant at least 8,000 hectares of forest per year to achieve 18 per cent of our land area covered by forest by 2050. Our new forests will be around for decades, and they must deliver for climate, nature, wood, people, and economic and rural development. This will require investment in the public and private forestry sectors to encourage and speed up the planting of diverse multifunctional and mosaic forests.
Confidence in the forestry sector is important given that it is a long-term investment and government support for the many ecosystem services, not just timber, that are produced from forests will be needed.
In the Fores research project, we are developing tools to map, measure and model the ecosystem services provided by different kinds of forests under different management regimes. Many of these ecosystem services are invisible but critical, as we expand our forests we need to be able to demonstrate their many values.
- Yvonne Buckley is professor of Zoology at Trinity College Dublin and co-director of the Co-Centre for Climate + Biodiversity + Water
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