Two somewhat related matters in New Zealand have influenced our thinking about including native forests in this discussion. 

Firstly, the exceptional rates at which the exotic radiata pine (Pinus radiata) grows in this country. A combination of a rather extraordinary tree backed up by sixty years of research, improved technology, and a very experienced and capable team of practitioners, has resulted in a tree and a forest with outstanding production and therefore carbon assimilation properties. 

Secondly, as already noted, native forest was removed from most, if not all, the fertile soils of the lowlands and our current impression of native forest growth is consigned to our most difficult country and reverting secondary forest.

Remarkably limited measures of carbon sequestration by native forests have been made in New Zealand. However, Tāne’s Tree Trust (TTT) has produced its Carbon Calculator for Planted Native Forest based on the Trust’s Indigenous Plantation Database (Bergin and Kimberley 2012). This database of measurements of planted native forest and shrubland is based around a comprehensive survey completed in 2010 from throughout New Zealand but also includes earlier measurements collected over several decades. 

Although many of the planted native stands represented in the database are small and have not been well managed, this database constitutes the largest and best available information on growth rates of plantations of native trees that we have in New Zealand with over 10,000 measured native trees and shrubs. Stand densities are relatively high with surveys targeting mostly single-species tree plantations with an average density of 1450 stems per ha. Shrubs were mixed-species plantings with an average density of 4075 stems per ha. 

Photo credit Alistair Guthrie @alistairguthrie

Measures of carbon sequestration in trees and forests are derived from the annual increase in stem, branch, foliage, and root mass, which includes a high proportion of molecular carbon. While different species of tree, and even the same species growing in different locations, may have somewhat different wood densities (and therefore different quantities of stored carbon), it is relatively easy to relate volume production in forests to tonnes of CO₂ stored per hectare. Methods for doing this are provided by Beets et al. (2012, 2014). Dividing this total by its age provides the growth and thus sequestration rate as a Mean Annual Increment (MAI) in units of tCO₂ ha^-1 yr^-1.

Because growth varies through the life of a tree, growth at a particular point in time is referred to as the Current Annual Increment (CAI) and is derived from measurements made over shorter intervals of time. As will be shown, this can increase markedly as trees become established.

In any situation or on any site there is a range of production that can be achieved by forests. At the low end (such as in very young forest or forests of slow growing species), annual rates of only 1-4 tonnes of growth per ha may be typical. With fast-growing species values significantly greater than 30 tonnes can be achieved. A range of 4-30 tonnes of CO₂ sequestration per ha per annum is probably typical of MAIs for New Zealand situations although rates outside this range do occur.

The Look-up Tables published by The Ministry for Primary Industries are used by small forest growers to estimate carbon stock for the Emissions Trading Scheme(ETS). The Look-up Table for radiata pine lists its carbon MAI over 50 years as between 21 and 27 tCO2 ha^-1 yr^-1 depending on region, which is recognised as at the higher end compared with what forests in other parts of the world can achieve. 

Only one Look-up Table is provided for indigenous forest, and this lists the carbon MAI over 50 years as 6.5 tCO₂ ha^-1 yr^-1. It is this value that many associate with native forest sequestration including planted native forest. However, this table was derived from measurements of naturally regenerating shrubland. A recent study of native forest carbon sequestration rates undertaken by Kimberley and Bergin (2021 in preparation) covers  various forest types ranging from naturally regenerating native scrub through to planted and managed native forest stands. This latter work represents the only measured native forest that is in any way comparable to the many thousands of biomass and carbon measurements made for radiata pine in New Zealand.

Importantly, this study clearly demonstrates that planted and managed native trees and forests exceed the Look-up Table rate of 6.5 tCO₂ ha^-1 yr^-1 by significant margins and it is clear that the Look-up Tables need to be adjusted to reflect this situation. The following sections summarise the results of this study firstly for naturally regenerating shrubland and forest, and then for planted native forest.

Photo credit Alistair Guthrie @alistairguthrie

Carbon sequestration rates by regenerating native shrublands are available from an inventory of New Zealand natural post-1989 forest carried out by the Ministry for the Environment in 2012 (Beets et al. 2014). The carbon MAI of measurement plots in this inventory ranged from 1.6 to 17.7 tCO₂ ha^-1 yr^-1 and averaged 7.0 tCO₂ ha^-1 yr^-1, close to the Look-up Table value. This inventory covered natural shrubland that has established since 1989 and therefore consisted of stands mostly less than 25 years old. 

Carbon sequestration rates in regenerating native shrubland covering a wider age range are provided from data collected by Bergin et al. (1995) in naturally regenerating manuka/kanuka shrubland in the East Coast of the North Island. Manuka dominates these shrublands until about age 15 years and then declines with kanuka becoming dominant. Carbon sequestration averaged about 10 tCO₂ ha^-1 yr^-1 over the first 20 years but then slowed considerably with little additional sequestration occurring beyond age 30 years (Figure 1).

While sequestration in manuka/kanuka shrubland declines rapidly after 30 or so years, regenerating climax species such as totara can often naturally enter the mix, eventually outcompeting the shrub species. Such species can continue to sequester carbon over many decades. Data from a study of naturally regenerating fully-stocked totara-dominant stands sampled in Northland (Bergin 2001), show carbon sequestration rates averaging 10 tCO₂ ha^-1 yr^-1 continue to be maintained over the 120-year age range covered by the study (Figure 1).

Figure 1. Carbon sequestration in regenerating manuka/kanuka shrubland on the East Coast of the North Island and in regenerating totara-dominated forest in Northland.

As most of the focus is on carbon assimilation by radiata pine in New Zealand, and with the data invariably from planted and managed stands, it is essential to compare like with like in an objective analysis. Data from the Tāne’s Tree Trust Indigenous Plantation Database  provides the most robust information available for planted native forest. 

Growth and yield information in planted stands containing the two most commonly planted native tree species, totara and kauri, show a trend of gradual increase as stands age. Growth is generally slower initially but increases at least up until the maximum ages of stands in the study, 70 years for kauri and 100 years for totara (Figure 2). 

On average, kauri stores carbon more rapidly than totara with an average MAI of 16.4 tCO₂ ha^-1 yr^-1 at age 50 years. Totara has a somewhat slower increase in carbon sequestration than kauri at a comparable age, with the MAI averaging only 10.0 tCO₂ ha^-1 yr^-1 at age 50 years, although this increases to 15.1 tCO₂ ha^-1 yr^-1 by age 100 years. The lower carbon sequestration rate of totara is in part due to its lower wood density compared to many other native conifers. 

Figure 2. Carbon sequestration in planted kauri and totara forests.

Of course, this data is still limited as planting is often still in a “trial” capacity, landowners have planted species of interest to themselves with less regard for provenance, the appropriateness of the site or the sort of silviculture that should be applied subsequently. Nevertheless, some work has been done which demonstrates that with attention to forest husbandry some even more impressive results can be obtained. 

Further analysis of the TTT database provides the table below which gives a summary of MAIs for a range of New Zealand species. Sequestration rates for planted kahikatea, rimu, puriri and beech are comparable to those of totara and kauri, with MAIs averaging between 10 and 15 tCO₂ ha^-1 yr^-1 at age 50 years (Table 1). For comparison, the Look-up Tables for radiata pine give average sequestration rates of 21 to 27 t CO₂ ha^-1 yr^-1 at age 50 years.

Sequestration rates of planted native tree species are low during the first few decades after planting with MAIs averaging only 3-6 tCO₂ ha^-1 yr^-1 at age 20 years. However, plantings of mixed native shrub species have much higher rates averaging 17.8 tCO₂ ha^-1 yr^-1 at age 20 years, partly because of the high stockings they are generally planted at, but also because many of these species have fast early growth. It is common practice to establish mixed plantings of native tree and shrub species with the shrub component boosting the early carbon sequestration until the tree species become dominant after several decades.

Table 1. Average carbon sequestration mean annual increment (MAI) of commonly
planted native tree species and mixed shrub species.

The carbon sequestration curves for planted tree species (Figure 2) show a trend of productivity increasing steadily with age. This increase in growth rates from age 30 years can be seen in Table 2 which shows CAIs by species and age. At 50 years, while totara is under 20, all other conifer and hardwood tree species have CAIs between 20 and 30 t CO₂ ha^-1 yr^-1.

Table 2. Average carbon sequestration current annual increment (CAI) of commonly
planted native tree species and mixed shrub species.

Photo credit Michael Bergin @mikeb_nz

A 102-year-old stand of planted totara in Northland with a stocking of 1640 stems per ha is estimated to have sequestered 1639 tCO₂ ha^-1 since planting, representing an MAI of 16.4 tCO₂ ha^-1 yr^-1.

A grove of kauri planted in 1963 in the Holts Forest Trust Sanctuary, Hawkes Bay. At 48 years old and a high stocking of 2000 stems per ha it is estimated to have sequestered 1100 tCO₂ ha^-1 since planting representing an MAI of 22.9 tCO₂ ha^-1 yr^-1.

The widely held view that New Zealand native forests are slower growing and accordingly slower to sequester carbon, as indicated by the MPI Look-up Tables, may be discouraging landowners from planting native trees, even where it is their preference to do so. Worse, it may be leading to planting advice that is incorrect and not helpful at a time when any form of tree planting by landowners is a bonus. 

Analysis of Tāne’s Tree Trust data from planted native trees still supports the position that radiata pine is initially faster growing and simpler to manage, but the difference between carbon sequestration in radiata pine and well managed planted native forest is much less than is often suggested. And investment in research and development would benefit native forestry as it has the radiata-pine industry, i.e., result in increased growth rates and more knowledge around forest management.  

New Zealand’s Carbon Look-up Tables for the Emission Trading Scheme should include the option for planted native forest as well as regenerating native forest. The current Look-up Tables for native forest are accurate when applied to naturally regenerating shrubland. However, to achieve good levels of sequestration over a long timeframe, regenerating forest needs to include climax tree species such as totara. 

Properly sited and managed planted native tree species are a good alternative where landowners wish to sequester carbon over long time periods, as well as enhancing natural landscapes, indigenous biodiversity and cultural values.

References

Beets, P.N., Kimberley, M.O., Oliver, G.R., Pearce, S.H., Graham, J.D., Brandon, A. 2012. Allometric equations for estimating carbon stocks in natural forest in New Zealand. Forests, 3: 818-839.

Beets, P.N., Kimberley, M.O., Paul, T.S.H., Oliver, G.R., Pearce, S.H., Buswell, J.M., 2014. The inventory of carbon stocks in New Zealand’s post-1989 natural forest for reporting under the Kyoto Protocol. Forests, 5, 2230-2252.

Bergin, D.O. 2001: Growth and management of planted and regenerating stands of Podocarpus totara D. Don. PhD thesis, University of Waikato. Unpublished. 316p.

Bergin, D., Kimberley, M. 2012. Nationwide survey of planted native trees Tāne’s Tree Trust. Technical Handbook. Technical Article 10.1.

Bergin, D.O.; Kimberley, M.O.; Marden, M. 1993: How soon does regenerating scrub control erosion?  New Zealand Forestry, 38(2): 38-40.

Bergin, D.O.; Kimberley, M.O.; Marden, M. 1995: Protective value of regenerating tea tree stands on erosion-prone hill country, East Coast, North Island, New Zealand.  New Zealand Journal of Forestry Science, 25 (1):  3-19.

Intergovernmental Panel on Climate Change. (2014). Technical Summary. In Climate Change 2013 – The Physical Science Basis: Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (pp. 31-116). Cambridge: Cambridge University Press. doi:10.1017/CBO9781107415324.005 

Kimberley, M.O..; Bergin, D.O. 2021: Rates of carbon sequestration in planted and regenerating New Zealand native forests. Manuscript in preparation.

Reed, A.H. (1953). The Story of the Kauri. A.H. Reed & A.W. Reed, Wellington, NZ. 439 p.

Issues with large scale reforestation

The Ministry of Primary Industries with its One Billion Trees Programme (1BT) and the Climate Change Commission (CCC) have advocated for large-scale establishment of permanent native forest to help New Zealand achieve its goal of being carbon-neutral by 2050 and to improve environmental, social, and economic outcomes. The expectation of successfully establishing tens of thousands of hectares of native forest a year is daunting.

There are major issues to consider when establishing native forest at such large scales using planting or natural regeneration. I have seen many examples of unsuccessful planting programmes, most due to not getting the basics right and especially a lack of the commitment and resources required to manage plantings over several years until at least canopy closure. A degree of realism is required in developing and implementing policies for successful establishment of native forest at scale. We do not want to over-promise and under-deliver.

Based on over 40 years of experience and using a similar format to a recent paper, ten golden rules are proposed to help policymakers, advisors and practitioners increase the success of large-scale native forest establishment in New Zealand.

Ten golden rules for establishing native forest

1. Protect existing forest ecosystems first

We need to look after what we have left and build from there

Eighty-five percent of New Zealand was clothed in native forest before the arrival of humans. Deforestation has had devastating environmental impacts. While 28% of our land is still in native forest, most of this is on upland sites not suited to other land uses. Much of this is highly modified and in decline or threatened due to introduced animals, invasive weeds, and biosecurity issues such as myrtle rust.

Even more significant is the almost total loss of lowland forest from productive landscapes now dominated by agriculture, plantation forestry and urban sprawl.  Remaining forest is often limited to degraded fragments.

As part of a holistic restoration programme for New Zealand’s native forest, we need to protect and enhance what we have left as repositories of local biodiversity, and pragmatically, as sources of seed and birds as vectors for restoration programmes. This includes fencing, pest animal and weed control, and by planting linking fragments to form corridors across agricultural and urban landscapes.

2. Identify appropriate areas for establishing native forest

Where is the problem, where is the land?

There are over one million hectares of marginal hill country. The Climate Change Commission (CCC) indicates most of this would benefit from reforestation. While exotic plantation forestry has often been the default option, there is increasing concern about the impacts of clear-fell harvesting on steep land. Together with long-distance haulage from remote locations to ports and mills, this makes exotic forestry on marginal hill country not only environmentally detrimental but also marginally economic or indeed uneconomic. Permanent native forest may be the best environmental  option for much of this land but is it realistic to expect tens of thousands of hectares of less profitable or uneconomic pastoral land to be retired from grazing per year for conversion to native?

There are also many opportunities for more native forestry in productive lowland landscapes further supporting current restoration programmes. These include enhancing existing remnants, establishing corridors linking remnants, planting riparian zones to improve water quality, establishing shelterbelts and shade trees, and extending recreational and amenity areas.

Priority areas need to be identified in collaboration with landowners, communities, iwi, and agencies for ramping up establishment of native forest and to be resourced accordingly.

3. Engage with landowners

Providing incentives for landowners is pivotal to any hope of land use change

With a proposed 25,000 hectares to be established in permanent native forest per year (CCC), the major hurdle will be convincing landowners to commit to large-scale conversion. Without buy-in by landowners, the area of marginal hill country and riparian zones required for establishing native forest at scale will not eventuate. While many farmers see the benefits of reforestation on less productive land, why should they retire pastoral land that continues to provide some income and adds to their bottom line? There are also significant ongoing costs too, so it is not just forgoing some income.

Many of the ecosystem services provided by native forests – reduced sedimentation of waterways, flood mitigation, carbon sequestration, improved water quality and biodiversity values – accrue more to downstream landowners and the general population than to the landowner retiring or planting the land.

The economic and environmental case for changing land use to native forestry needs to be made to landowners. How can we make permanent native forest cover pay? Incentives potentially include:

• some form of biodiversity credits as promoted byTrees That Count and others
• carbon credits
• industries based on non-timber forest products such as honey
• in the long term, the option of selective harvesting of high-value timber under a continuous cover forestryregime whilst retaining high forest values.

Equally is the need to engage with all stakeholders in any discussion about large scale land use change to more permanent native forest including local communities, iwi, managing agencies and the general public.

4. Work with nature and time – natural regeneration

What can we do to help nature do it for us?

Despite many years of research into reducing the establishment cost of natives, the cost of blanket-planting native forest is still about 10 times that of planting radiata pine. In reality, it is not feasible to restore tens of thousands of hectares of native forest by planting alone. New Zealand’s native forest has a remarkable ability to regenerate naturally. So, what can we do to help nature restore marginal land and riparian areas to native forest?

An understanding of the natural successional processes in native forest can guide us in how we can assist natural regeneration of native forest in degraded landscapes. Most sites will require some combination of fencing to exclude grazing stock, control of pest animals including those that predate on our birds and reduce seed production and spread, control of invasive weeds, and supplementary planting to provide seed sources for tree species that have become locally rare.

Assisting natural regeneration is far cheaper and easier than planting and is the only practical option for large-scale reforestation of permanent native forest. Succession back to native forest can be hastened by strategies such as planting ‘seed islands’ – groves of key canopy tree species that will attract birds. Mimicking nature in the selection of hardy shrub species as nurse cover, will in time allow later successional high-forest tree species to be introduced, either via planting or natural regeneration (if seed sources are nearby).

5. Get serious with planning, resourcing, and time scales

We need to lift our game in planning, resourcing, and implementing native afforestation

If we are to take up the advantages of economies of scale, we need to get serious about planning and supporting the infrastructure required for large-scale establishment of native forest. This is not a business for community groups alone – we need professionals involved at all stages, including ecologists to determine what is required to promote natural regeneration, and practitioners experienced in planting natives and controlling weeds and pest animals. Community planting is suitable for small, accessible sites, but large-scale planting and remote areas requires contract planters experienced in native planting and management. I despair at any notion that a major lift in establishing more native forest can be done by our already hard pressed volunteer community.

So, let’s get serious with the business of increasing permanent native forest. This includes:

• the need to start planning early including practicality of planting vs regeneration,
• seek advice of restoration ecologists and experienced practitioners who have a track record of successful establishment of native forest on sites like yours,
• order seedlings from native plant nurseries with a history of providing good quality eco sourcedstock, and
• develop a management plan suited to your site, objectives and resources.

Paramount to success is an understanding that natives require extended and additional maintenance compared to exotic forest and that this essential post-planting care needs to be planned and resourced so that it is economically sustainable.

6. Get the basics right

Most native plantings fail due to lack of attention to the basics

Do your homework. There is a lot of information out there as well as local experience in planting and managing native forest for multiple purposes. In my 40 years of applied research with experience in auditing dozens of planting projects each year, I find there are still too many planting projects where the basics of good planning, site preparation, use of quality seedlings of appropriate species, good planting technique, and timely management and monitoring have not been thought through and adequately resourced. Check out successful local restoration programmes and find out how they did it, including issues encountered and pitfalls they avoided – warts and all!

For the inexperienced, test by establishing a small trial first before expanding to a larger scale. This will quickly provide you with a realistic indication of the commitment and resources required to successfully establish native forest. With this experience, you can expand your planting programme in subsequent years. While you are building up valuable information from a small-scale pilot, ensure the remainder of the site to be planted is in a holding pattern (e.g., continued grazing) that will maintain it ready for restoring forest.

Don’t put all your eggs in one basket.  Plant different sites over several years to spread risk and avoid major losses due to factors like drought. Some factors can come out of left field and damage your plantings, so take time to find out what the issues will be.

7. Give nurseries a fair go

Native plants don’t materialise overnight – ramping up production needs time and resources

Even though natural regeneration may take the heavy lifting for the tens of thousands of extra hectares proposed to be established in native forest per year, planting will still need to be a major component. Native plant nurseries have seen boom and bust cycles in planting and are reluctant to expand to accommodate any increase in plant production without forward ordering and deposits to ensure they are not left yet again with unsold stock. The recent survey of native plant nurseries and action plans by the New Zealand Plant Producers Incorporated (NZPPI) highlights the challenges facing the industry with many nurseries expanding their business in the past few years, and some with capacity to grow further. However, the overall challenge faced by the industry in scaling up requires supply chain coordination between landowners, industry organisations, nursery sector and government.

The question of support for start-up new community and iwi-based nurseries versus providing support for those existing native plant nurseries interested and with capacity to expand production is also one of many issues. We have all seen how competitive the native plant nursery is even for long established nurseries like the Taupo Native Plant Nursery and Oratia Native Plant Nursery, both closing just as the Billion Trees Programme started. And there are smaller community nurseries struggling to maintain quality and retention of skilled management and workers once the initial start-up capital has been exhausted. We need to avoid a race to the bottom in producing low-cost plants at the expense of good quality eco-sourced seedlings to meet requirements of planters.

Nurseries require at least 12 months notice to ramp up production and for some of the slower-growing tree species, at least two years lead time is needed, longer in southern regions. Multiple species are often involved with different seed collection times and with annual fluctuations in seed crops, so start talking to nurseries early.

On top of this, there is the need to ensure planting stock is of high quality, eco-sourced and fit-for-purpose in terms of the right species for the right site planted at the right time. It is up to those paying for the seedlings and funding the planting to check seedlings are meeting requirements. You get what you pay for – cheap, small or end-of-season stock may be a bargain but may not survive on your site.

8. Monitor success

Assessing performance provides insight into how to do it better

Systematic recording of the performance of your planting project is essential to determine whether your restoration initiatives are meeting objectives. This information will help you modify management practices to improve success and provide you with a track record demonstrating your success to funders when seeking further support.

Monitoring needs to be done from the day after planting – there may have been a rabbit or deer that took out your palatable species within the first 24 hours, so you need to know what the issues are as they happen, not six months later when evidence of how seedlings died has long gone. Timely weed and pest animal control before your planted natives are swamped by weeds or eaten by animals can only be scheduled using a well-planned monitoring programme.

The success of planting programmes should be measured on what has successfully established at least two years after planting, or better still when canopy cover has been achieved, rather than on how many seedlings were planted during the working bee! Be flexible – modify your management based on the performance of last year’s endeavours.

9. Thinking of innovative solutions? Test them out first!

It’s OK to think outside the square but be wary of those that have a deal for you!

Many different options including high-tech ones are being promoted for reducing the cost of establishing native forest. It is good to keep an open mind and to look for site-specific solutions using local resources and site factors to assist successful planting and encourage natural regeneration. But be wary of new technology as the saviour – it is often over-rated, expensive, energy-hungry to produce, potentially polluting, and impractical on a large scale – and often promoted by those wanting to sell you something! The best option with a new product or method is to test it out on a small scale first. This allows you to determine if it will be practical and cost-effective before implemented at a larger scale.

Many innovative ideas, while site specific, are not high-tech. These include:

• the successful use of gorse as a nurse for regeneration of native forest as demonstrated by Hugh Wilson and his team at Hinewai Reserveon Banks Peninsula.  . But it can be site specific too – gorse mixed with aggressive vines like blackberry and old man’s beard can persist for decades
• grazing can be a tool to help establish the relatively unpalatable manuka, kanuka and totara on steep hill country
• establishing ‘seed islands’ to enhance establishment of diverse high forest on a large scale is also worth exploring as part of large-scale reversion
• and there is a lot of debate and unknowns about the potential for using exoticssuch as pines and eucalypts as a method of establishing native forest, especially with carbon in mind.

There is considerable interest and research underway in direct seeding, drones to deploy seed and seedling bombs, and biodegradable pots for raising plants in nurseries to reduce plastic waste. In addition, there are a myriad of consumables such as stakes for relocating planted seedlings, tree protectors to reduce rabbit browse and increase shelter on exposed sites, weed mats and mulches to reduce soil water loss, fertilisers to boost growth and hydro-gels to extend moisture availability in dry periods. Some of these have proved their worth on some sites. For your site, it is good to see ‘with’ and ‘without’ comparisons of such add-ons in planting trials or test them yourself first on a small scale and compare with your standard practice. These extras take time to implement in the field, come at a cost, and may need maintenance and retrieval to reduce pollution. So, check they will provide you with greater success.

Consider easier solutions. For instance, if rabbits and hares prove impossible to control completely, then consider planting a larger proportion of less palatable species to get initial cover, or see if regrowth of tall grass, while not swamping your plants, deters rabbits – they don’t like wet backsides!

10. Keep your ecological gains

Ongoing resourcing is essential for sustaining ecological gains

The practical challenges and costs of the long-term management of existing and regenerated native forest are high and continue long after establishment, in fact will never stop. Unfortunately support for the costs of pest and weed control, fencing and maintenance is limited after native forest has been restored. We become complacent thinking the job is done, but maintenance and management of our restored and existing ecosystems needs to be sustainable – back to Golden Rule 1.

Funding sources are critical as a source of ongoing funds for the maintenance of new and existing healthy indigenous forests and their long-term sequestration of carbon, and contribution to biodiversity and freshwater ecosystems. Funders often want to fund something new rather than maintain existing projects yet our ecological gains must be sustainable and resourced accordingly. Once pest animal and weed control stops, ecological gains are quickly lost so it is imperative that long-term funding strategies and mechanisms are developed to maintain healthy, diverse restored indigenous ecosystems as habitats for our endangered plants and animals on both private and public land.

Establishing native forest requires integration

Successful large-scale establishment of native forest will depend on working with nature and better integration of those involved. Encouraging natural regeneration can only be done in tandem with pest animal control to prevent damage of establishing seedlings, working with Predator Free NZ, neighbouring landowners, iwi and local communities to boost bird populations and seed production for a diverse forest ecosystems, selective weed control to remove or reduce the most aggressive and persistent exotic species, and undertaking targeted supplementary planting to bring back once abundant species now locally extinct or scarce.

New Zealand’s forests are remarkably resilient. They have survived aeons of changing climate and geological and volcanic catastrophes but now they need our help, something that takes time – years or even decades. Restoring a fine cloak of native forest over our whenua requires us to work together, work with nature, and take the time.

Dr David Bergin

New Zealand’s current growth model is approaching its environmental limits, largely due to intensification of land use. Our biodiversity is under threat according to an OECD report on our environmental performance. The report recommended land management measures to reduce water pollution, and a broadened use of economic instruments to provide incentives for conservation on private land. Extinction rates for our native fauna are among the highest in the world.

In addition to this, we will continue to see intense weather events which highlight major issues with clear-fell forestry operations in sensitive steepland catchments. The plantation forest industry’s social licence to operate is under question – there have been persistent calls for vulnerable hill country to be established in native forest.

Putting Nature into the economic equation

Ecosystem services are defined as the benefits people obtain from ecosystems, or ‘natural capital’. This is an anthropocentric construct to help factor the value of ecosystems into the economic equation – to aid decisions about utilisation of natural resources, or undertake activities that may impact on ecosystems.

Non-timber values

Aside from timber production, New Zealand’s economy relies on forests for a myriad of non-timber values (NTVs), i.e., all elements of ecosystem services other than wood products.

Quantifying NTVs is vitally important for leveraging the business case for afforestation with native species. However, NTVs have largely not been factored into the economic value of forests because of the lack of awareness of the wider value of forests, as well as difficulty in tracking and quantifying the myriad of products and services.

NTVs in sustainably-managed native forests have been researched by the authors of this opinion piece. All statements are fully referenced in a much larger work. NTVs were evaluated under four main categories (note that there are overlaps with some values potentially falling into more than one category).

(i) Non-timber forest products

Industries associated with non-timber forest products are currently underdeveloped in New Zealand, except for mānuka honey, mānuka oil, and sphagnum moss. Many non-timber forest products are produced by small businesses that are often economically important for local communities and have potential for further development.

Non-timber forest products include:

• honey and other bee products (native forest species provide essential early-season nectar flow vital to the apiary industry)
• rongoā (traditional medicines), nature-based pharmaceuticals
• forest understory crops, including kawakawa
• wild foods, freshwater fisheries, hunting and trapping of wild game.

(ii) Environmental regulating services

Our economy relies heavily on forests (natural and planted) for environmental regulating services. However, they are widely regarded as ‘free of charge’ or a ‘gift of nature’.

These ecosystem services include:

• carbon sequestration – the only environmental service currently monetised
• habitat provision and enhanced biodiversity values (in terrestrial and aquatic environments)
• services provided by urban trees, including air quality, green infrastructure, and climate regulation
• stabilisation of soils, erosion reduction, catchment protection, and coastal buffers
• retention of nutrients, nutrient recycling, and water quality
• pollination services  – vital to the horticultural industry
• green firebreaks and fire risk reduction.

(iii) Socioeconomic, cultural and spiritual services

Forests provide general amenity and ambient environments for outdoor recreation and tourism, and have important spiritual and cultural values. Natural environments and native species underpin our unique sense of place and our international reputation. However, these services are particularly difficult to quantify in economic terms.

These ecosystem services include:

• ambient environments for tourism (particularly ecotourism), outdoor recreation, hunting, fishing, and wild foods
• cultural values associated with native forests, including conservation of native species and kaitiakitanga, rongoā, mahinga kai (traditional food sources), and tūrangawaewae (sense of place)
• aesthetic/landscape values
• native trees, green space, and human well-being in urban areas
• forest-based livelihoods and training opportunities
• ‘Clean, Green’ NZbrand image, political and commercial reputations.

(iv) Underlying supporting services

The original concept of ecosystem services includes supporting services that underlie the rest of ecosystem services. This includes photosynthesis and soil formation, and several other services that overlap with environmental regulating services, including water and nutrient recycling. Care needs to be taken to not ‘double count’ overlapping ecosystem services.

The benefits of weaving native forest back into our rural landscapes

Sustainably-managed native forests deserve a much higher profile as an economically viable land use in New Zealand. This could legitimately be achieved with the inclusion of NTVs in economic analyses.

While many NTVs can be attributed to forests irrespective of whether they are native or exotic, in most cases, the aggregated NTVs of native forests would likely be greater than that for exotic plantation regimes – particularly for cultural and spiritual values, conservation of indigenous biodiversity, and protection of erodible land, water quality, and downstream infrastructure and ecosystems. Permanent native forests managed solely for NTVs or sustainably managed under continuous cover regimes, are likely to have the highest aggregated NTVs, which could potentially exceed timber values.

Native forests in riparian areas are likely to have the highest aggregated NTVs because of the following services:

(i) buffering of the negative impacts of plantation forestry operations, intensive agriculture and urban development through prevention of sediment loss, recycling of nutrients and protection of water quality;

(ii) decreased run-off and flood peaks, protecting downstream infrastructures;

(iii) increased biodiversity and cultural values due to habitat provision, creation of wildlife corridors, protection of aquatic habitat and traditional food sources;

(iv) creation of connections between ecosystems to enable seasonal migrations;

(v) pollination services for adjacent horticultural and agricultural industries; and (vi) increased landscape aesthetic values.

The integration of sustainably managed native forests into rural landscapes provides opportunities for new and more appropriate primary production and business models for the future. For example, native forest could be woven back onto steep, erodible slopes and riparian areas on farms for all the benefits they provide. This could include sustainable harvest of high-value timber via continuous cover forestry regimes, while retaining the environmental and cultural services associated with high forest.

The farming community has come under increasing pressure regarding social licence to operate and is subject to increased regulation by local and central government. Restrictions on land use and nutrient run-off have recently been introduced to improve and protect water quality. Bringing native forest back onto farms – particularly in riparian areas and on erodible, marginal land – will improve environmental outcomes and regulatory compliance.

The draft advice from the Climate Change Commission recommends establishing new permanent native forests on steep, marginal farmland to offset the long-lived gas emissions in sectors with limited opportunities to reduce emissions from 2050, e.g., offsetting nitrous oxide emissions from agriculture. The Commission also recognises the many other benefits that this would bring, including improving water quality and erosion prevention.

NTVs in native forests on private land are currently difficult to monetise, other than carbon sequestration and some non-timber forest products such as mānuka honey. There is the conundrum of ‘valuing the invaluable’, i.e., NTVs with no direct material benefits and therefore difficult to incentivise, but critically important, nonetheless.

Incentivising native forestation – who benefits, who pays?

The One Billion Trees Programme signifies that the New Zealand Government recognises the wider value of forests; to date they have  committed to funding two-thirds in native species. Also, amendments to the NZ Emissions Trading Scheme (ETS) have strengthened the carbon market, providing greater incentive for all types of afforestation. However, native forests have been handicapped by the ‘one size fits all’ MPI look-up tables, which in some circumstances under-estimate the carbon sequestration by  native species.

Protecting existing forest and increasing permanent forest cover are recommended as top priorities for climate change mitigation and adaptation in New Zealand and globally. In their draft advice, the Climate Change Commission recommended a shift from clear-fell radiata pine to permanent native forest in erodible hill country.

There is also the well recognised problem of under-representation of lowland natural ecosystems in the conservation estate, due to intensification of land use for agricultural and urban development . And the value of forest cover for human well-being in urban areas has increasingly become recognised. Aside from the many environmental and cultural benefits, there is scientific evidence that access to green spaces makes us happier and healthier.

Weaving more native forest back into our rural and urban landscapes will greatly benefit New Zealand’s economy and human well-being, as well as Papatūānuku. However, there is the question of ‘who pays, and who benefits?’ 

While in general, the majority of costs associated with establishing and managing native trees on private land fall to the landowner, the benefits of NTVs often accrue to a much wider community, including:

• locally, e.g., amenity services such as shade and shelter, increased soil stability, biodiversity enhancement, hydrological services, and landscape aesthetics
• catchment-wide, e.g., reduction in erosion and sedimentation, improved water quality and water flow regulation, and increased resilience to intense weather events including protection of downstream infrastructures and ecosystems, and biodiversity enhancement
• regionally, e.g., catchment protection, biodiversity enhancement, increased tourism and employment
• nationally, e.g., accumulative benefits associated with all the above mentioned NTVs, and New Zealand’s international branding as a clean, green country
• internationally, e.g., carbon sequestration and mitigation of climate change.

There is a compelling argument for compensating the efforts of private landowners who safeguard biodiversity in the wider public interest, which is the flip side of the ‘polluter-pays’ principle.  Native forests generally support a greater biodiversity of indigenous fauna and flora than exotic forests, with most fruit and nectar feeders largely dependent on native forest for habitat. Currently efforts are underway to create a biodiversity credit system to incentivise establishment of native forest in New Zealand.  Initiatives to increase biodiversity values will likely drag other NTVs up as well.

The opportunity for New Zealand is to incentivise afforestation with native species on privately owned, rural working lands, and reward landowners for providing NTVs, particularly with the high cost associated with successfully establishing and managing native forest. The models to do this urgently need to be developed.

The Climate Change Commission recommends that the Government implement measures to incentivise establishing and maintaining at least 16,000 hectares of new permanent native forests per year by 2025, increasing to at least 25,000 hectares per year by 2030. These levels of new planting could be assisted by extending grant schemes such as One Billion Trees or by developing ecosystem services payment schemes.  Another longer-term option is to invest in research and development in continuous cover forestry regimes, and development of a sustainable niche timber industry for high-value, farm-grown native timbers.

Dr David Bergin

Dr. Jacqui Aimers

Gerard Horgan