In Norway, there is a lack of long-term empirical studies to assess what potential effects intensified forest management has on water quality and quantity, although a few studies have been conducted historically (e.g. Haveraaen 1981) and more recent studies have focused on soil solution parameters (Clarke et al. 2018a). Studies from other boreal and northern temperate countries might also be applied to Norway, although care might need to be taken because of differences in forest management between countries even when the natural conditions are similar. In a recent study Futter et al. (2019) made an overview assessment of forest management effects on surface water quality using a modified version of the DWARF framework (Futter et al. 2016). The methodology was adapted to the three main climate mitigation measures and Norwegian environmental conditions. Potential effects on surface waters were here assessed on three temporal scales: 1 year after harvest, 10 years after harvest and 100 years after harvest (Futter et al. 2019). It is important to highlight that the measures proposed by the Norwegian government might not give a noticeable environmental effect directly after implementation, but effects might occur many years later and upon forest harvesting. A challenge in this respect is a general lack of long-term (one rotation or more) field experiments, making it hard to test long-term modelling empirically.
Forest management impacts surface waters in Norway, but the severity of the impact is dependent on what type of forest harvest method is used and on what temporal resolution the negative effects are evaluated (Futter et al. 2019). Any evaluation of environmental consequences of a measure must consider the whole rotation period from initial planting to harvest. The most visible and long-lasting effects of forestry occur at final harvest (Akselsson et al. 2007; Zetterberg et al. 2016), and usually not during afforestation, replanting or fertilisation, although measures can also have immediate, but short-term consequences for water quality (Löfgren et al. 2016).
We will in the following assess the three climate mitigation measures that Norway has launched for the forestry sector. By assessing how these measures have been received by the forest actors, and the extent to which water is safeguarded, we will point at possible weaknesses and uncertainties in the way these schemes have been devised and put into practice.
Afforestation on new areas
Government support to afforestation on new areas was introduced in 2015 as a three-year pilot project in the three counties Nord-Trøndelag and Rogaland (from 2015), and Nordland (from 2016). These three pilot regions are chosen to represent three different climatic regions of coastal Norway. The initial scheme was set up to support planting of forest on new areas with NOK 15 mill for the first of three pilot years, and the measure is a continuation of earlier and ongoing attempts at facilitating afforestation in coastal regions of Norway. In a report on coastal forestry from 2008 the potential for afforestation is shown by recommending that 500 000 ha in the coastal region of Norway is afforested within the next 50 years (Øyen 2008). A more realistic, yet ambitious, estimate indicates that 2 500 ha of new forests could be planted within the next 20 years at a national level (Haugland et al. 2013). The reception of this scheme was slow, and considerable effort by regional authorities has been put into convincing forest owners of potential economic and climate gains, and also identifying suitable areas for planting. During the 5-year pilot a total of 628 ha was afforested in these three counties, spread across 189 holdings (Bøe et al. 2019).
Afforestation as a climate mitigation measure has been extensively criticised by environmental NGOs as well as scientists, due to concerns relating to the negative effects on biodiversity by planning to use the Sitka spruce (Picea sitchensis), known to be an alien and invasive species (Backman and Mårald 2016). Concerns relating to impacts on cultural landscapes have also been raised, and that utilising these areas for forestry would constitute an irreversible regrowth on areas that could be used for food production, pastures, tourism and recreation. These debates made the Parliament request changes to the scheme, and in the national budget allocations for 2015 four additional criteria were added to the pilot phase: (i) the use of native Norwegian tree species (most commonly the main commercial tree species in Norway, Norway spruce, Picea abies, (ii) planting should take place on open areas and areas in early regrowth state, (iii) afforestation should only be on areas with high production potential and where there is a low expected change in the albedo effect (estimated in Nordland county by comparing global radiation data with maps for duration of snow cover, (iv) planting should be done on areas that are unimportant for biodiversity, recreational interests, cultural heritage or cultural landscapes (Haugland et al. 2015; Bøe et al. 2019).
In the environmental criteria developed for this initiative, it is stated that afforestation on new areas can impact environmental values, such as water quality (Haugland et al. 2013). However, beyond mentioning that forests have potential impacts on water flow in a watershed, only terrestrial environmental criteria are considered in detail. Water-related concerns appear neither in discussions concerning the potential benefits nor in those concerned with problems associated with afforestation. Another reason for why water quality is not taken into account in the development of environmental criteria might be that there is not sufficient relevant baseline data for Norway. There are only a few early studies addressing the potential effects of forest management on water quality (e.g. Haveraaen 1981), and some more recent ones focusing on sea-salt episodes and acidification (Larssen and Holme 2006) and mobilisation of mercury (e.g. de Wit et al. 2014). Most studies on forest management effects have not monitored surface waters and much focus has been on the effects on soil water. With the relatively low number of Norwegian studies, it is more difficult to determinate the potential impacts related to water quality as the Norwegian conditions may differ from other Nordic countries. Moreover, any effect will depend on local conditions as there are considerable differences within the country.
At a general level, afforestation can, however, have significant regional and stand-level consequences for soil and surface water acidification. Forested land generally receives higher amounts of atmospheric deposition of acidifying substances, also called the forest-filter effect (Mayer and Ulrich 1977). In addition, forest growth in itself has an acidifying effect (Tamm and Hallbäcken 1988), due to hydrogen ions replacing base cations taken up by trees. Potential acidification appears not to have been considered in the afforestation scheme, except in relation to change of tree species to Norway spruce (Haugland et al. 2013).
From a Norwegian perspective, the proposal to afforest large areas of coastal land may result in a significant increase in sea-salt related acidification events. In Norway, already forested areas receive about 10% more sulphate deposition and 18% more inorganic N deposition compared to open areas, in what is named “forest-filter” effects (De Schrijver et al. 2007). Excessive deposition of sea salt can result in pronounced short-term depression of pH in surface waters due to cation exchange processes in the soil (Wright et al. 1988; Hindar et al. 1995). Afforestation in Norway can have substantially negative effects on surface waters with regard to mercury, base cations (calcium, magnesium, potassium and sodium), dissolved organic carbon (DOC) and nitrogen (Larssen and Holme 2006; Berthrong et al. 2009). These effects will occur over a long temporal scale. Positive effects of afforestation in a 100-year perspective are likely with increased carbon sequestration and greenhouse gas (GHG) reductions (Futter et al. 2019).
Afforestation is, however, a measure that falls within existing forestry regulations and standards, including requirements for buffer zones. The typical buffer zone along rivers and waterways according to the Norwegian PEFC standard is 10–15 m, while some conditions warrant up to 30 m, although there are exceptions allowing for narrower zones. The standard also state that ground preparation before planting should not be conducted in areas set aside as buffer zones or within 5 m of existing streams with a yearly discharge. In addition, there is also a possibility that increased terrain transport leading to erosion and runoff to rivers and streams has immediate consequence for water quality, if best cutting practices are not adopted.
From our assessment of this scheme, the extent to which water is safeguarded rests on whether the environmental criteria are complied with and the extent to which the forest industry’s own standards (PEFC) with regard to ground preparation, planting and cutting and water considerations are adhered to. However, while the potential effects from afforestation on water quality might be insignificant in the short run, there is less certainty with regard to the long-term effect of such a measure.
Increased stocking density of existing forests
Increased stocking density of existing forest areas was introduced as a support scheme for climate mitigation in 2016. The initiative seeks to contribute to increased capture of carbon by increasing the production capacity of existing forests after harvesting, either through planting with higher densities or supplemental planting, in a context where stocking density in Norway is often below the optimal level (Søgaard et al. 2015). For the years 2017–2019, 80% of costs for planting of up to 500 plants per ha was reimbursed to forest owners with forest areas that are beyond a minimum plant density threshold depending on “site index” (NAA 2019).
Although presented as a climate-policy measure, increased stocking density as specified by the Norwegian Agriculture Agency, is part of the ordinary silviculture activities, and does not imply changes to how forest areas are managed (NAA 2019). This measure therefore falls under the forest sector’s existing regulations, so that environmental values are also here safeguarded with reference to the national Regulation on Sustainable Forestry (LMD 2006) and the forest industry’s PEFC standard. According to the Norwegian PEFC standard environmental values are to be registered before harvesting, important environmental values and biotopes are to be protected, buffer areas to water bodies are not to be planted, and general outdoor and use interests of the general public are to be heeded.
In addition, it is a requirement that any planting supported through this initiative is mapped accordingly, to ensure that regulations are followed, and further so that control and evaluation can be carried out. The Agency does, however, acknowledge that control of stocking density is difficult and must be based on discretion. We consider that this makes it unlikely that sanctions against forest owners that do not comply with the set guidelines are implemented.
The support scheme has, however, only to a limited extent been utilised by forest owners. This might be a result of complicated procedures for getting support, and that the benefits for the forest owners have not been clearly communicated, as too high plant density also comes with certain risks. When trees are planted at too high densities, self-thinning often occurs due to increased competition for light, water and nutrients (Futter et al. 2019).
However, due to these set environmental criteria and the limited reception, increased stocking density of forest plantations is unlikely to have a substantial effect on water quality and quantity in Norway in the present context.
Of the three climate mitigation measures for the forestry sector that we assess here, forest fertilisation has had the most popular reception. In the Nordic context, nitrogen (N) fertilisation is commonly used 5-10 years before felling in moderately N deficient forests so as to increase the biomass (Rytter et al. 2016). The fertilisation supported through this scheme is the application of 150 kg of nitrogen per ha 10 years before harvesting (NAA 2016). With this initiative, Norway saw a remarkable increase in fertilised forest areas, from 700 ha nationally in 2015, to 8 379 ha, 9104 ha, and 5648 ha respectively for the years 2016, 2017 and 2018 (SSB 2017, 2019). This is not unprecedented as the Norwegian forestry sector also had periods of high levels of nitrogen fertilisation in earlier times. The 2016 level has, however, not been reached since 1967. Most of this fertilisation (~ 70%) took place in Hedmark in the south-eastern part of Norway, a county known to be the stronghold of forestry.
Forest fertilisation is, and has been, a contested practice (Lindkvist et al. 2011). The main goal of fertilisation is increased production of tree biomass, but through the addition of nutrients fertilisation also has several potential direct and indirect effects, as fertilisation may impact on biodiversity through changes in vegetation and species composition (Strengbom and Nordin 2008; Hedwall et al. 2010, 2013; Sullivan 2018); it may cause shifts in microarthropod communities in the soil (Lindberg and Persson 2004), and can lead to changes in GHG dynamics (Metcalfe et al. 2013). Laudon et al. (2011) points to the potential consequences that fertilisation may have on water quality and the ecology of water bodies. The magnitude and scale of these effects all depend on the application scheme chosen, i.e. the amount of nitrogen added at what time during the growing season. Also, while forest fertilisation might not have noticeable environmental effects immediately, there can be substantial effects on surface water quality upon forest harvesting, depending on which forest harvest method is used (stem-only, whole tree-harvest, light/heavy machinery, etc.) (Futter et al. 2019).
Studies have shown that nitrogen fertilisation leads to detectable short-term increases in soil solution N concentrations (Clarke et al. 2018b), and can also increase N concentrations in streams draining fertilised areas (Laudon et al. 2011; Haugland et al. 2015). The increased N can affect surface water acidification and studies have identified changes in aquatic plant community composition, with a shift towards more N tolerant species (Haugland et al. 2015). However, given the high demand for N in most Nordic forest surface waters, water quality effects are hard to detect even a few hundred meters downstream of fertilised sites (Schelker et al. 2016). Fertilisation with wood ash is currently not allowed in Norway (Regulation on Fertilisers of Organic Origin), but a field experiment has shown no clear short-term effects of wood ash spreading in forests on soil solution chemistry (Clarke et al. 2018b).
In the white paper of 2012, in which forest fertilisation was proposed as a climate mitigation measure, it is stated that the initiative should come with a set of environmental criteria (KLD 2012). These criteria are stated in a joint report from the Norwegian Agricultural Agency and the Norwegian Environment Agency (Haugland et al. 2014). Based on the potential risk that fertilisation might pose to water bodies that are or have been prone to acidification from long-range atmospheric pollution, a protective zone was established for the coastal regions in southern and southwestern parts of Norway. The assessment of environmental criteria sets an upper limit for the 5-year pilot period of fertilisation of 2 500 ha of forests within this zone. During the first year of the pilot, 1 200 ha were fertilised within the protective zone, which is almost half of the total allocation for the trial period. For 2017, another 900 ha of forests were fertilised within the zone, which left some 300 ha for the rest of the trial period. No such restrictions apply to the area outside of this zone, and the extent of the measure is here limited by the annual allocation of funds over the national budget.
However, for fertilisation of forests, both inside and outside of this zone, regulations apply on which areas are to be fertilised (cutting class and vegetation class) and what buffer zones should be adhered to. The Norwegian PEFC standard requires a fertiliser-free zone of 25 metres around lakes, rivers and streams, to minimise nutrient loss and leakage. Mapping has a crucial role for the fertilisation scheme and how it safeguards environmental values. During implementation, environmental values such as surface waters and sensitive or protected nature types are considered through official mapping tools. After validation by the forestry cooperative—sometimes including field visits—these same maps are used for the application of fertiliser by helicopter. These operations produce a track-log that is further presented to the local and national authorities for checking that the requirements are complied with. The municipalities are formally responsible for receiving the applications for reimbursement, and should make sure that necessary documentation is presented, that the operation is mapped, that necessary environmental considerations are taken, and that areas that should not be fertilised are not. That the scheme relies so heavily on maps and mapped datasets, digitalised GPS and fertilising mechanics is key for the way in which the scheme is understood as well as in line with set environmental criteria. While the municipalities have the formal responsibility for ensuring that the environmental criteria are complied with, in practice, however, this is to a large extent left to the forest cooperatives, suggesting a level of uncertainty regarding how the municipalities carry out their responsibilities vested in the Forestry Act.
Hedwall et al. (2014) argue in their analysis of constraints and opportunities for intensifying forestry through fertilisation in northern boreal forests that fertilisation at the moderate scale—comparable to current practice in Norway—would have only small and temporary effect on the environment, but would generate a high rate of return for forest owners. This is also reflective of how the forest fertilisation initiative is perceived by some key actors in this complex, as a win–win situation in terms of economic benefits to the forest owners and climate gains.
As the fertilisation operations to a large degree rest on these environmental criteria set by the authorities and the standards for sustainable forestry, and in practice ensured by the use of official maps indicating sensitive environmental values, as well as the automated operation of application of fertiliser in line with these criteria and maps, we consider the risks for impacts on surface water from the forest fertilisation at the point of initiation to be minimal. This is less certain for the longer term.