Eucalyptus Conversions: 3 Case Studies

A lot of people have asked us how we would go about transforming a eucalyptus or a pinewood into a biodiverse forest. And as always, when it has to do with forests, there isn’t a one-size-fits-all solution. So, we thought we’d explore a few projects we’ve worked on in the past that attempted to do just that. We’ll give some quick background and then look at the pros and cons of each approach to get a sense of how they behave.

Before we start though, if you’d like to get a bit clearer idea of why we’re focusing on eucalyptus you can take a look at this previous post about eucalyptus in which we explore its dangers, benefits, and what to look for when designing around it.

1. Bramble’s Hat

Bramble’s Hat is a small plot of land (500m2) near Santiago that had been repopulated with pines and eucalyptus about 30 years ago after the last fire passed through. In the last few years, however, due to new fire legislation in Galicia that said that these species could not be grown within 50 meters of a house the entire wood had to be cut. In that space, we designed a system of productive agroforestry that could be managed in about a day or two a year, and harbor small productions of a few nut-butters, jams, and apple cider.

Here, the challenge resulting from the presence of pine and eucalyptus was the highly degraded and acidic soil. What we opted for was to transform the soil through the native undergrowth, while the productive species would mature within it. The native undergrowth would build soil, as we cut it back in strips about 2-3 times a year, while we the ‘productive species’ slowly become established between them.

Pros

  • A clear plan for succession – Understands not only how undergrowth will respond once the old eucalyptus is cut, but also has a clear plan to guide the transformation of the soil.
  • Builds soil – By allowing the undergrowth to grow back strong for a few months before being cut, and not trying to maintain a lawn between the trees, the system is able to create organic matter and build soil.
  • Balances the soil – By allowing many different types of roots and species to become established in the ecosystem, and by building soil, the acidity and negative consequences of eucalyptus can be remediated.
  • Biodiverse – Seeks to create a healthy and resilient ecosystem through balancing a variety of native and productive species.
  • Works within current legislation – Provides a positive outcome and possibility for how to replace stands affected by new legislation.
  • Buffer against fire – The density of the moist green growth can create a store of water that can resist low and medium-intensity wildfires.
  • Strong economic possibility – Through the eventual sale of the products it’s designed to create, this land can not only pay for itself but greatly outcompete the money eucalyptus would have produced.
  • Low management – By allowing nature to do the majority of the regenerative work, this frees people to do less work.

Cons

  • A staircase for fire – Due to the progressive rise between the strata (small bush to large bush to tree) there is a clear path for fire to take from the ground into the canopy. Thus, a high-intensity wildfire would be able to do significantly more damage.
  • Slow response to acidity – Choosing a passive response to the acidity of the soil may slow the growth of the productive species by a few years. This could have been easily solved by mixing a bit of lime into the soil.
  • Requires good fertility – This type of plantation, due to the species it’s choosing to replace the eucalyptus requires good soil or access to water in order to thrive. Attempting to establish this forest in a place with worse soil would require either a few more years of soil building before attempting to establish productive these species, or a change to more drought-tolerant species.
  • High difficulty in design – Due to the biodiversity and response to environmental factors, this type of forest might not be easily adapted to another space. It is a local response to the local environment.
  • Must be managed by hand. – Because of the high density of the plantation, there isn’t enough space for tractors to pass. This could be easily remedied by adapting the design by spreading out the species. However, this would also decrease the quality of the soil, as tractors would further compact the soil.

2. Tapada

Near Ponte Barca in Northern Portugal is about a hectare of land that began its life as a pine and eucalyptus wood. The idea was to transform it into a biodiverse native forest that would serve as a companion space to a B&B being built on the land.

Interestingly, instead of cutting the entire wood at the same time and then planting the new forest in its place, the conversion will take place over the course of a few years. By removing about a third of the eucalyptus and pines each year, while planting 1200 trees under the cover of the mature trees that are still left. This is an attempt to mimic a bit more how nature creates a forest. Over time, as large trees fall and light filters into those younger trees, they will grow and take their space. Also, the majority of those 1200 trees will be cut back leaving the strongest trees to establish the mature forest.

Pros

  • A strong plan for ecologic succession – Loosely mimicking how nature prefers to move from one type of ecosystem to another, this forest will transform slowly over the course of a few years instead of all at once.
  • Biodiverse – With 17 types of primarily native trees being planted, fauna will find this an interesting place to take refuge.
  • Shade – By keeping a portion of the trees standing each year, the presence of older trees will provide some of the benefits that a mature forest would otherwise provide for younger trees as they become established. Those are shade in summer, protection against wind, and an ability to hold onto humidity longer.
  • A direct response to acidity – By planting each tree with a small amount of lime, the negative effects of the acidity created by the pine and eucalyptus are weakened.
  • Overplanted – Natural forests will often see thousands of trees planted where only one or two mature trees will eventually stand. Overplanting allows us a selection of the strongest trees best suited to their conditions, allows for more trees to fail, lowers overall management, and accelerates the establishment of relationships with soil microorganisms.
  • Builds soil – Once those overplanted trees are eventually cut and incorporated back into the ground, they will provide a strong source of fertility for the soil.
  • Resilient – Plantations that prioritize native species can usually be done on weaker soils with less water, and with less active management. This increases the range of land that can be used.
  • Economically viable – Thanks to the added value the presence of the forest will provide for the B&B, this can compete with eucalyptus economically making it an interesting alternative.

Cons

  • Difficulty to harvest trees – By spreading the cutting of established trees over the first few years, a situation is created in which these trees become harder to cut and harvest each year without disturbing the plantation. Here, this is eased by two factors. The first is the overplanting of trees which lowers the impact of a few of them getting squashed by falling trees. The second is the choice to harvest the largest trees first and progressively cut smaller and smaller trees.
  • Must be managed by hand – For the first few years, due to the strong slope of the landscape and style of plantation, management is complicated. Though the style of plantation does mimic nature, it is not a natural system and still needs our help to become established. Since there is no easy access for tractors, trees will have to be watered by hand and the brush cleared away by hand.
  • Low productivity – Due to prioritizing native species, only a few will be able to feed humans, and the lodgers in the B&B wouldn’t be able to be fed from the forest (Although fauna will most likely be very happy).
  • Soil Acidity – For as long as there is a considerable population of pine and eucalyptus the negative effects they have on soil will continue.
  • Closed canopy – Due to the high density of trees, the structure of the forest will not allow much light to filter down for the growth of an understory. This will lead, overall, to a less diverse environment.
  • Medium-difficulty in design – When working with native species who are more attuned to our climate, their survival is more likely, and design becomes a bit easier. The difficulty here comes from matching each species to the niche that is most to their liking. (i.e. drought-tolerant species in the driest soils, shade-tolerant in the shadiest, and so on).
  • Depleting soil – By selling the wood from the trees that are cut, organic matter that might have built the soil, is brought away, and the ecosystem is weakened.

3. De-eucalyptization

A de-eucalyptization is an event that’s exactly what it sounds like. People will organize an event in which they go around cutting large eucalyptus, pulling out small ones by the roots, and otherwise weakening the species’ dominance over an ecosystem. They hope that by removing the eucalyptus the natural forest will take its place. The better events will take place simultaneously with a tree planting, or take place somewhere where a native forest is already growing beneath the eucalyptus.

Pros

  • Economic Benefit – This can often include a concrete plan for how to use the wood for an immediate economic benefit. This often involves selling the wood, or converting it into mushrooms.
  • Prioritizes Native Species – There is a clear plan for replacing species behaving invasively with native species which will have healthier interactions with the local environment.
  • Easy to design – In most cases, the only steps are to cut back all the eucalyptus and either allow the natives to grow or plant new natives.
  • Lower Fire Risk (Long Term) – By eliminating the eucalyptus and allowing a native forest to establish, over time, this will create a barrier that protects against wildfire.

Cons

  • Weak Long Term Plan – Often, these events are planned as singular events and lack a long-term strategy to ensure that the work of the day is protected.
  • Dependent on Management – Eucalyptus is an unrelenting species that will grow back from its roots time and time again. And until a forest capable of shading them is established, they’ll continue to grow. In short, de-eucalyptization efforts are building a dependence on frequent community actions that may not always be able to commit to the transformation. This creates a distrubance in an ecosystem without follow-through.
  • A weak plan for succession – Eucalyptus often grows where soils have become weakened to the point where many native species do not want to grow on that soil. Simply removing eucalyptus is not a natural succession and does not solve the underlying ecologic problems harming an ecosystem. It’s often the case that de-eucalyptization events do not provide a strong plan for how to improve the soil to the point where it will support a native forest on its own.
  • Low economic return – Since most plans do not prioritize establishing long-term economic, this makes this type of action unappealing to a lot of people who do not yet see the inherent value of a forest.
  • Occasionally dependent on herbicide – Eucalyptus is notoriously difficult to get rid of. This has driven some actions to use a heavy amount of herbicide to remove the eucalyptus. This further poisons an already damaged soil.
  • Treats Eucalyptus as the root of the problem – By singling out eucalyptus as a purely negative species, it makes us unwilling to take advantage of some of the benefits that eucalyptus has to offer.
  • Higher Fire Risk(Short Term) – By eliminating the majority of the canopy cover all at once, the understory is given as much light as it needs to thrive. Without active management, conditions are being created to actually give wildfire the fuel it needs to spread.

You’re Transformation.

What we hope this post will make clear is that there is no single response to eucalyptus. Each piece of land, just like us, is an individual with individual needs and potential.

If you’re considering converting a eucalyptus wood into a biodiverse forest and you’d like a bit of help in the process, feel free to get in touch!

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