Human-Induced Regeneration

What do human-induced regeneration (HIR) projects involve?

HIR projects are supposed to involve the regeneration of permanent even-aged native forests through changes in land management practices, particularly the cessation of clearing and reducing grazing pressure by livestock and feral animals.

The projects do not involve planting seedlings or seeds – proponents are expressly prohibited from planting trees. The forests are supposed to grow through natural regeneration (e.g. from soil seed stock and in situ seedlings) as a consequence of changes in land management.

Proponents of HIR projects do not directly measure tree growth. Instead, regeneration is modelled using the Australian Government’s Full Carbon Accounting Model (FullCAM). No measurements of the amount of carbon that is sequestered in the regrowing trees are required at any time, by either the proponents or the regulator.

What are HIR projects supposed to look like?

The HIR method was designed to incentivise the regeneration of native forests by allowing juvenile trees and shrubs to regrow in areas that were previously comprehensively cleared. The method is supposed to work by paying landholders to stop land management practices that inhibit regeneration like re-clearing and intensive grazing.

The areas that are credited should have originally sustained native forest, and this forest must then have been lost due to clearing or another event. After the project began, forest cover should increase.

When looked at from above, the areas that are credited should look something like the images in Figure 1 below, when they start and finish.

One image on the left showing cleared land. One image on the right, of the same piece of land, showing regenerated tree cover.
Figure 1: Project start (left), Project finish (right)

To have integrity, it is important that the areas that are credited in HIR projects reflect this ideal. Sites that look like the images in Figure 2 below when they start are problematic and are likely to have low integrity – the credits issued to these sites are unlikely to represent real and additional abatement.

One image on the left showing sparse tree cover. One image on the right, of the same land, showing slightly denser tree cover.
Figure 2: Project start (left), Project finish (right)

There are two reasons for this.

Reason 1

The model that is used to estimate tree growth and carbon storage is an area-based model (FullCAM). It models the even-aged regeneration of a forest across the entire area that is credited. The model is based on two assumptions. The first is that the area being credited contains no (or very few) mature trees and shrubs on the site when the project starts. The second is that the regenerating forest then grows towards its maximum carrying capacity, as per the images below.

Figure 3: Modelled regeneration

Problems arise if the credited areas already contain mature trees and shrubs when the project starts. In colloquial terms, projects will get carbon credits to regrow trees that were already there. This is referred to as over-crediting; projects will receive more credits than there is additional tree growth. The extent of over-crediting depends on how many mature trees and shrubs are on the site when the project starts. The greater the number of pre-existing trees and shrubs, relative to the locations potential tree cover, the greater the over-crediting.

Reason 2

The amount of regeneration that can occur on an area of land is a function of its site resources (e.g. water and nutrients) and the number of mature trees and shrubs that are already there. The reason for this is that existing trees and shrubs compete with new growth for site resources and, in doing so, reduce the amount of new growth that is possible. As a result, areas that contain fully intact remnant vegetation will not be able to sustain additional trees and shrubs over the long run because the site will already be at or near its maximum carrying capacity (the total amount of trees and shrubs that a site can sustain).

Where an area contains partially disturbed remnant vegetation, it may be possible to restore it and sequester carbon in some additional trees and shrubs. However, adding additional trees and shrubs to a partially disturbed area is not the same as regenerating an even-aged native forest across the entire area. Because of the way the model works (see above), the projects will be over-credited. Also, to the extent there is regrowth in areas of intact native vegetation, it will be unclear whether the growth is due to rainfall or the project activities (reducing grazing pressure from livestock and feral animals).

In the desert and semi-desert rangeland areas where most HIR projects are located, tree and shrub cover fluctuates through time with rainfall. Droughts can trigger significant tree death, and wetter times encourage new growth. These rainfall-induced fluctuations in tree and shrub can occur over long periods of time, extending many decades.

If projects are allowed to be located in areas of remnant vegetation – even areas that are partially degraded– the method should have rules that ensure projects are only credited for additional tree growth induced by changes in grazing management. Projects should not be credited for tree growth that is merely a product of rainfall variation: this is non-additional, it would happen anyway.

The HIR method does not have measures to control for the impacts of rainfall variability when estimating the sequestration that is attributable to the project activities. To address this issue, the HIR method requires every land area that is credited to satisfy the following requirements.

  • It must have forest potential, or the ability to achieve and sustain forest – in practice, this requires the area to have sustained forest in the past and the forest must have been lost at some point from clearing or another event.
  • Regeneration must have been suppressed (stopped from regenerating) by grazing pressure, re-clearing or another relevant suppressor during the 10 years prior to the registration of the project (the ‘baseline period’).
  • It must be reasonable to expect the proposed reduction in grazing pressure, or other activities to address relevant suppressors, are necessary to regenerate the area.
  • The credited areas must not contain significant numbers of mature trees and shrubs at project commencement. This is because it is not possible for mature trees and shrubs to have been suppressed by grazing pressure or clearing during the baseline period. Similarly, it is not possible for regeneration from soil seed stock, in situ seedlings, rootstock and lignotubers to occur in areas that already contain mature trees and shrubs.  

Areas that satisfy these requirements will look like the ideal in Figure 1 above.

If areas look more like Figure 2, there is a significant risk they will be over-credited and that any credited sequestration will be non-additional. This applies even when there is new tree and shrub growth in the credited areas. The fact there is new tree and shrub growth does not mean it is a product of the project activities.

It might simply be due to an above-average period of rainfall. To test whether the growth is ‘additional’, it is necessary to compare the observed growth to what is happening outside of the project area, in the surrounding landscape.

Only when tree and shrub cover has increased relative to what was there when the project started and relative to what has occurred in surrounding areas can there be confidence the abatement is both real and additional.

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