Permaculture and the Edible Forest Garden: a Critical Analysis

I’ve been interested in the edible forest garden idea for over twenty years and have planted and designed several myself in Ireland in that time, and visited several others. But they have never lived up to my expectations and were largely unproductive, despite sourcing as many perennial vegetables and other interesting edible plants as I could. Here I review the claims made for them and what evidence there is to support the idea- and conclude that, as Permaculture founder Bill Mollison said in the first place, in temperate regions you are far better growing your fruit trees and vegetables separately.

Temperate permaculture– is this a passing fad, an idealist’s hobby or is there a case for wider promotion of the practice?

  • Introduction- Design By Nature: Permaculture and the Forest Garden Concept

 “Permaculture” – derived from permanent agriculture – is a concept of sustainable land use and design coined and developed by Bill Mollison and David Holmgren in 1974. Mollison defined the concept as:

The conscious design and maintenance of agriculturally productive ecosystems which have the diversity, stability, and resilience of natural ecosystems

 (Mollison 1988).

 Since then, permaculture has grown into a worldwide movement of activists and designers applying permaculture principles to the whole of society (Holmgren 2002). Permaculture is more an approach or philosophy than any specific technology, but where it has come under academic scrutiny, many of the kinds of practices frequently advocated have been found lacking in supporting evidence (Chalker-Scott 2010).

In this essay we shall focus on one of the best-known expressions of permaculture design, the edible forest garden or food forest for temperate regions, which are designed with the intention of mimicking the structure and functions of natural woodlands. Successful integration of trees with agriculture for multiple environmental and crop protection functions, nitrogen fixation and fodder is well established in traditional systems in many parts of Europe (Rigueiro-Rodriguez et al 2009), and is gaining renewed interest today as an essential part of agricultural sustainability. It is worth examining why, then, while forest gardens continue to be popular amongst the permaculture fraternity and the sustainable food movement, they have attracted little academic research, and very little uptake by farmers, orchardists or market gardeners. As we shall see, evidence to support the claims that forest gardens achieve both low inputs and high yields is lacking, and there are good theoretical reasons why the concept is unlikely to succeed in temperate zones.

  1. Definitions, Origins and extent of current practice

 Edible forest gardensalso known as forest gardens, woodland gardens, food forests or analog forests have been defined as “a perennial polyculture of multi-purpose plants” (Jacke 2005) and are comparable to the multistory agroforestry systems common across the tropics known as homegardens (Kumar and Nairn 2006). Robert de J. Hart is generally credited with being the first to bring the concept to Europe in the 1980s when he started the UK’s first forest garden in Shropshire (Hart 1996). He cites as his influences Smith (1950), Yeoman (1971) and Sholto Douglas (1985), and his work in turn went on to influence Patrick Whitefield (1996) and Martin Crawford (2014) in the UK and Jacke and Toensmeier (2005) in the US.

Based on the definitions used by the authors cited above, for this essay we will define edible forest gardens as:

Gardens which are primarily or entirely perennial polycultures, containing at least three identifiable vertical layers of food-bearing plants including trees, shrubs and perennial herbaceous understory.

 This definition differentiates them from both annual vegetable gardens as well as other well-established agroforestry systems such as broad-scale silvoarable systems, which generally include only one or two annual crops in between rows of trees (Rigueiro-Rodriguez et al 2009).

Crawford (2014) estimates there are some 800 hectares of forest gardens in the UK and lists approximately 160 forest gardens in his Forest Garden Network, including 9 in Ireland, 30 in Europe and a handful in the US. They range in size from small gardens of as little as 50 square meters to smallholdings of up to about 5 hectares, with the smallest area for a “fully functional” forest garden estimated at around 1000 square meters.

Perhaps ironically given their continued popularity in permaculture, Mollison did not himself advocate perennial edible forest gardens for temperate regions. He was well aware that temperate gardening was characterized by annual or biennial seed crops and tubers and by the need to store root vegetables over the winter, and that tree crops are more likely to be for fruit than for staples (Mollison 1988). The academic literature also indicates that temperate gardens have traditionally tended to be based on annual vegetables, often arranged in relatively formal beds and generally requiring full sunshine (Ninez 1987; Vogl and Vogl-Lukasser 2003).


Despite this, Jacke and Toensmeier (2005) cite the ancient practice of coppicing of woodlots for firewood and poles as an example of traditional forest garden practice. However, coppice woodlands are not primarily food gardens, and generally only involve one or two layers, the coppiced hazel and sometimes a standard timber crop. In the UK, orchard trees were commonly grown with an intercrop of soft fruit—blackcurrants or gooseberries—prior to 1955; less commonly some (mainly annual) vegetable crops were included, and there are examples of intercropping between trees with annual vegetables (Kumar and Nairn 2006). One of the few examples that do meet the definition of a three-layered system included asparagus as a perennial vegetable (Newman 1986, citing Fekete 1958), but apart from these cases it seems unlikely there was any widespread traditional practice of genuine three-story perennial edible homegardens in Europe or the US.

In a recent effort to correct the dearth of research on edible forest gardens, the UK Permaculture Association began a 10-year forest garden trial in 2009, publishing a baseline survey of 117 forest gardens in the Europe and the US in 2013 (Remiarz 2013, 2014). The oldest sites were started in the 1980s, with the majority starting since 2000. Nearly half reported that “food self-reliance” was their main objective, with the majority saying this has been largely achieved, though what proportion of each gardener’s food requirements was met is not quantified. In fact, the species lists suggest that in reality the crops grown in most of these forest gardens differ little from the fruit and green vegetables typically grown in traditional home gardens from the 1950s (Ninez 1987).

This apparent mismatch between aspirations and practice requires some explanation: why are forest gardens still believed in and promoted—at least within the permaculture fraternity—if the practice falls so far short of expectations? To answer this we now consider the philosophy of copying nature underpinning the forest garden concept.

  1. Philosophy: Return to the Garden?

 Along with other more recent influential permaculture writers (Crawford 2005, Jacke 2010), Hart (1996) saw planting forest gardens as not only a practical way of growing food but also about ushering in new ways of living and seeing the world:

My mini-forest is the culmination of many years’ study and practice of the system that has come to be known as Agroforestry or Permaculture, and which many people, including myself, believe has a major role to play in the evolution of an ‘alternative’, holistic world order. A Green World. The World of Gaia.

– Robert Hart (1996)


The belief underpinning permaculture that “nature knows best” and agricultural systems are best shaped in the image of the natural world stems from the “organismal metaphor” proposed in the early 20th Century (Clements 1916), seeing ecosystems as behaving like a “super-organism,” and on Odum’s cybernetics, seeing ecosystems as analogous to machines (Odum 1981, cf. Holmgren 2001). Conservationists such as John Muir then popularized these ideas of an ideal state of “natural balance” for both nature and man (Marris 2011), but while still a dominant idea in both popular culture and much environmental policy (Botkin 2012), most ecologists today see natural systems as being characterized by continual change and adaptation rather than any ideal state of stability, and some suggest that the ecosystem concept itself may have outlived its usefulness (O’Neill 2001).

Permaculture and other alternative approaches to farming are rooted in the post-1960s counter-culture’s beliefs about the need to prepare for an inevitable collapse of industrial society and a consequent return to subsistence farming (Gold and Hanover 1987). Botkin (2012) traces this idea of a “Fall” and “Return to Eden” back to the roots of Judeo-Christianity, a powerful metaphor that also helped shape early ecology and environmentalism. Perhaps these deeply held cultural beliefs help explain the ongoing interest in close-to-nature approaches to farming such as forest gardens, which are seen as a way of restoring a presumed ideal state of natural balance that humans have disrupted by clearing the forests and tilling the land.

  1. Design Principles: Diversity, Complexity and Balance

There is a common-sense appeal to the permaculture concept of mimicking nature. Unlike a conventional annual vegetable garden with its ongoing needs of digging, weeding and applications of fertilisers, forest gardens are intended to be self-maintaining, with minimum inputs or labour, and to function with the diversity, complexity and the perceived “balance” of a natural woodland while conveying the following advantages (Hart, 1996; Jacke 2005; Crawford 2010):

  • the trees make use of vertical space which in principle would allow more food to be grown in the same area;
  • perennial plants don’t require annual tilling of the soil and planting of new seeds;
  • the diversity of polycultures should reduce problems with species-specific pathogens;
  • mulches and nitrogen fixing plants, common to other agroforestry practices obviate or reduce the need for fertilizer applications;
  • diverse systems are more resilient due to greater complexity;
  • forest gardens have multiple functions and yields including therapeutic and environmental benefits.

Taking each in turn we can establish theoretical explanations for why these principles in themselves are insufficient to make forest gardens viable as alternative food production systems.

Vertical space

 Yields from tree crops are limited by a trade-off between yield produced and the energy used by the tree itself in maintaining its woody structure. In addition, while yields increase over time as the trees grow larger, they will also produce more shade and roots (which will extend at least as far as the leaves), both of which are likely to reduce the yield of understory plants via competition for light, water, and nutrients. Crawford recommends up to 50% wider spacing than in conventional orchards to allow enough light through to the lower layers, and so most of the advantages of the vertical space are lost. We will compare figures for yields of tree crops and arable crops below.

 Annuals vs Perennials

 Perennials have the advantage of not requiring annual cultivation and planting, and often emerge earlier in the spring than their annual counterparts, but have the disadvantage of being static and not easily changed in response to changing conditions. By contrast, annual crops can reach optimal yields within just one or two seasons, and an annual system is much more flexible in that a different variety or crop can easily be switched to in the event of disease, climate change or even nutrient depletion. Annual grains were the first plants to be domesticated for the very reason that, in setting seed each year, they have lent themselves to dramatic improvements for yield and other traits through plant breeding (Kingsbury 2009).

Monocultures vs polycultures: Diversity and Intercropping

 Diversity is one of the “principles of permaculture” (Holmgren 2002) providing the notional underpinning for forest gardens, yet this diversity may compromise yields. The competition between species has already been noted. Also, polycultures lend themselves less to mechanization of cultivation and harvest, and nuts that fall from trees are likely to be lost in any groundcover vegetation. However, some researchers have pointed to the work already done on intercropping—traditionally practiced around the world—as a basis for promoting more complex polycultures such as forest gardens (Gowland 1996; Watson 1998). Resource partitioning (soil and light), the ability of combinations of crops to access more soil nutrients than monocrops, and modification of the microclimate, have been shown to increase yields compared to the individual crops grown alone. (Vandermeer 1989, Innis 1996).

While intercropping has also been shown to increase yields in relatively simple silvoarable systems such as vegetables between fruit trees (Newman 1986), Vandemeer also found cases where yields were lower if inappropriate crops were chosen. Whitefield (2013) was also aware of this, pointing out that the largest gain from intercropping is gained from the first crop addition and is likely to decline with the addition of each subsequent crop. In a review, Denison (2012) found that achieving optimum spacing in intercropped systems was difficult, and that while intercropping increased yields compared to the average of the two crops, they were often still less than the best crop grown as a monocrop. Thus, for many farmers the pragmatic choice was to grow the single best yielding crop alone.

The apparent lack of variety in the crops we eat is also cited as a reason to prefer forest gardens over conventional agriculture, but there are good reasons why only some crops have been adopted apart from ease of improvement breeding mentioned above. Being readily storable and transportable, corn, rice and wheat alone account for nearly half of humankind’s calorific intake. Another reason is pollination- a crop suitable for agriculture requires reliable methods of pollination to produce good yields, and so these grains tend to be either self-fertile, pollinated by many different insects, or wind pollinated, in contrast to many other plants that have co-evolved with specialist pollinators (Warren 2015).

Efficiency: inputs and outputs

Along with Jacke, Crawford (2014) argues that it is the efficiency of the system that acts of a measure of sustainability, not the total yield. He claims that modern agriculture often achieves an energy return of 5:1, and sometimes less than 1, with more energy going into the system than coming out, while forest gardens can achieve as much as 40:1. Even if this were true in terms of absolute physical energy- it is not explained how these figures are arrived at- fertilizer accounts for only about 2% of global energy consumption and farming without it would be far more labour-intensive and require up to four times the land to grow the same amount of food (Smil 2011). Thus, while low-input systems may be less dependent on fossil fuels overall, this advantage is vastly outweighed by the land-sparing benefits of continued increases in production from modern agriculture.

Systems, resilience and complexity

 Permaculture advocates the importance of the number of connections between elements in a design, arguing that such diversity of interactions leads to greater resilience: if one synergistic relationship breaks down, plenty of others are there to pick up the slack and prevent system failure. Natural systems are presumed to be in a natural “balance” which can easily be disrupted, with a change to one part unbalancing the whole system

Yet according to Denison (2012), an evolutionary perspective applied to agriculture reveals that natural systems have evolved more by chance than by any design (Gleason 1926) and that the defining unit in terms of function, adaptability and resilience is the individual species and not the system as a whole. Plant assemblies in nature may be as malleable as in a designed garden, readily incorporating newcomers in the form of aliens, invasive or naturalized plants and often continuing to function well even after the loss of many native species (Wilkinson 2004).

Multiple functions- habitat and therapy

Other kinds of “yields”, such as the aesthetic and therapeutic value of gardening and working close to nature, are often cited as highly valued reasons for promoting forest gardens (Hart 1996; Jacke 2005). There is no question that these are important aspects of gardening, but may be served as well if not better in other ways. Urban gardens, though not primarily for food, already provide habitat for a wealth of biodiversity (Goddard et al 2010). Equally, there is good evidence that gardening and gardens have great therapeutic value (Haith 2015) but again, there is no reason to suppose edible forest gardens will significantly add value to this.

  1. Yields- Land Sharing or Land Sparing?


 Despite absence of data, claims for high yields produced in such temperate permaculture systems can be extravagant (Sustainability Centre 2015). Hart (1996) for example states that “the forest garden is the most productive of all forms of land use”, supporting some of the most densely populated countries on earth. This might be plausible in tropical climates, at least in terms of total biomass production if not food yields, but the limitations of light and the relatively narrow range of productive tree crops available in temperate zones make this an unlikely scenario for the UK.

Comparative yields of staple crops

In the UK, most food produced in forest gardens is fruit or leafy green vegetables. Yet for forest gardens to prove their worth in production terms, they need to compete with other staple crops with high value of protein and carbohydrates. The main option for tree crops here is nuts.

Cobnuts (hazelnuts) can achieve yields of 3.5-4 tonnes/hectare 8-10 years after planting (CALU 2006), walnuts potentially 1tonne/hectare and sweet chestnuts up to 4.75 t/ha (Crawford and Newman 2006). This is still a long way from typical UK yields for barley and oats of 5-6 t/ha or wheat over 8 t/ha (DEFRA 2014). Potatoes can yield over 40 t/ha  (FAOSTAT 2013) -assuming 80% water content, this would equate to 8 t/ha in dry weight.  These best-case values for nut trees in the UK are not found in forest gardens with a complex understory, but generally in monocultures. Additionally, nut yields in the UK vary from year to year and are vulnerable to poor weather during pollination or early wind-fall (Crossland 2013) and hence are unlikely to grow much beyond their current niche market.

Discussion of yields is important because the driving rationale of the forest garden is that modern agriculture is unsustainable, laying the blame at the feet of monocultural systems based on annual grains and pulses. However, despite often well-founded fears of soil erosion and nutrient depletion, global yields of these crops continue to increase through improved varieties and technology (Ausubel et al 2012; Grau et al 2013). Indeed, total land used for agriculture may have already peaked (Our World in Data 2015) as a result of ongoing improvements in efficiency, and substantial area of land has been “spared” for nature as a result (Stevenson et al 2010). This dramatic and sustained increase in agricultural productivity over the past century has resulted in only 2% of the population in the U.S. being required to farm (AFBF 2015). In these respects then, modern farming is arguably more resilient because of its continual innovation and adaptability.

 6. Conclusions

 The three—or more—layered perennial edible food forest we have examined here is an attempt to improve agriculture and food production by mimicking nature. What works well in the tropics however does not seem to work well in cooler climes. While interest and research into sourcing promising novel crops and new cultivars from around the world continues, most temperate forest gardens seem little different from the fruit gardens and orchards commonly found in Britain prior to the 1950s.

Temperate forest gardens do offer great potential for further research on plant interactions within multi-strata perennial systems, and there is great scope for improvements in cultivars of many tree crops. A warming climate may offer a greater range of possibilities for novel crops to be grown in the UK, as is being tried, for example, by Otter Farm in Devon where they are now growing olives and almonds, but it is as yet unclear whether multi-tiered systems will provide any significant advantage.

Despite the lack of promise forest gardens show in becoming a viable alternative to industrial farming, the ongoing interest in permaculture philosophy together with public concern about sustainability will ensure that they continue to be experimented with by enthusiasts. The myth of the need to return to a “balance with nature” remains a powerful influence in many areas of public policy well beyond the permaculture movement and will continue to shape ideas about food, farming and conservation for a long time to come.


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Forestry Study Tour

Last week was the study tour for some 40 Bangor MSc Forestry students who traveled by coach to the Lake District, the Scottish borders and North Yorkshire to see a range of sites demonstrating Continuous Cover Forestry (CCF), rewilding and flood mitigation. The theme for the week (and subsequent essays we will have to write): the Resilient Landscape. Here is a brief review of the week with some photos and descriptions of the sites. Apologies for any mistakes or ommissions, this is largely a quick write-up of notes taken during the visits.

Day 1 Wythop Forest Continuous Cover Forestry, Lake District.

Gareth Browning of FC England was our host for the day, and explained the management of 156 ha of mixed forests under CCF.
CCF has been practiced in much of the forest here since 1980, with douglas fir as the main species, and there are some impressive specimens (for the UK!!) of up to 52m tall. These areas are now under transition to broadleaf as they fall under the Plantation on Ancient Woodland Site designation (PAWS).


The markets for the Douglas fir are mainly in Germany where it is used in port infrastructure; some also goes for ships masts. The Workington paper mill 

has provided a new market for wood chip, used to power the mill, making thinnings and better forest management more viable. Douglas fir is worth 2-3 times that of Sitka spruce as timber.

There are 16 separate forests in the area, ranging in size from 9ha to 1000ha. The lack of connectivity is a mixed blessing: for example, about 120 roe deer are culled every year, and the separation between the forest areas makes this much easier since roe tend to cover a large area; red deer would be more problematic since they would rarely break cover.
A significant constraint is the proximity of the A66: safety regulations require a minimum of two tree lengths in distance between any public road and tree felling; since CCF requires large seed trees to be grown, this distance becomes quite large. When felling within this limit takes place the road needs to be closed for some weeks- an expensive proposition.
CCF is fairly new here, just 30 years, compared to 300 years in Switzerland for example. In the last 10-20 years, the forests have begun to regenerate themselves.
Douglas fir needs a certain degree of warmth and sun for the seeds to germinate- it will not regenerate on north-facing slopes and requires underplanting here. Other species being introduced now include western red cedar, silver fir and Montgomery pine.
Large Douglas fir  frame tree surrounded by thicket of regeneration which will subsequently be thinned
One advantage of CCF is that it produces more wind-firm trees (although on other sites we learned that CCF for spruce is not practical for windy sites- any thinning leads to more windthrow, for spruce at least). Larger trees can develop good buttresses for stability. A more diverse structure is the aim. About 50 frame trees are retained per hectare, which works for shade tolerant species such as Douglas; more than that and it becomes hard to maintain a diverse structure with gaps that can regenerate.
Some plantation forest has now been designated ancient woodland, influencing future management plans and species choice. Increased species diversity is favoured for resilience to future pests and diseases and climate change. One species mix is beech, planted under conifers. As with other sites we visited, most larch here has succumbed to Phytophthora ramorum and has been felled.
Gareth argued that forests will be increasingly valued for other reasons, recreational and flood mitigation perhaps, and should be at least as deserving as subsidies as farming.
We drove round to nearby Dodd wood where the recreational value was obvious. Osprey viewing stations bring in £1-2million to the area annually. The birds need a diverse structure, with the precise species being unimportant. Some of the frame trees will be left to continue to grow with no plans of harvesting- visitors to the park appreciate this since “Big trees make us feel very small.” They have a Wow factor.
There was some discussion of the difficulties of extraction for very big trees close to the road or on steep slopes. In some cases helicopters might be considered. But the extraction process, although disruptive to the soil, creates a seed bed leading to more regeneration. Even opportunities for windthrow can help this and the end result is a “self-healing” forest. Ultimately however, small areas of CCF are not enough.
Stunning view from the hostel in the morning
Day 2- visit to the Eddlestone water project with Hugh Chalmers of the Tweed Forum. This is for flood mitigation involving engineering meanders into the river, planting trees, bank stabilization, log flow restrictors. To access the land used in this project, some £2.3million has been paid to farmers in the area either in compensation of land purchase. Hugh pointed out that it is not just the trees, which can help reduce flooding through increased water infiltration, but also the vegetation growing beneath them. Fish benefit from up to 50% shading of the water by trees. The project also benefits from carbon credits for carbon sequestration, though some of the land is peat bog and might be better left unplanted. Hugh made the wry comment “there is nothing logical in land management- people love peat for growing trees in [as a potting medium]!” The possible role of beavers was mentioned (not in this area at present) but that their beneficial effects could be replicated partly by growing willow on the riparian zone and regularly coppicing it- beavers apparently only use fairly small material (like willow coppice) for their dams, while constructing log flow restrictions would use bigger material which could cause a problem if large logs moved downstream rapidly in a flood. Impressive to see something of how this kind of project can happen in practice. As we have also seen on the course in North Wales, the key issue is successfully working with many stakeholders, especially the farmers with land along the river. As High said, it is good to get farmers working together and thinking in terms of the whole catchment.

Glen Tress Trial Area

This Forestry Commission forest is half way through a 120-year transition process from single-aged stand Sitka spruce to CCF with diverse age structure and mixed species.

From the FC website:

When the Trial Area was established in 1952 most of the plantations were 20-30 years old.  The 117 ha area was divided into six Blocks and the plan was to transform the area over a 60 year period by felling and regenerating groups totalling two hectares in each Block every six years.
Various different mixes are being trialed in different plots, with the prevailing philosophy of “anything but Sitka”. The problem is, as we were to find in other sites also, is that Sitka regenerates so vigorously that it is a major headache trying to establish anything else. On poor land, it even regenerating under itself is problematic as it tends to come up so thickly it gets checked and fails to thin itself, simply not growing. In some cases the most efficient thing is to simply mulch the entire seedling crop and plant into the bed of mulch.
Glentress is also the preeminent site in Scotland for mountain biking. Some of our group opted for a mountain bike session rather than the forest tour, but I decided to see the forest this time. There was considerable discussion about the challenge of combining hosting  quarter-of-a-million mountain bike visitors with the practice of felling large trees. A minority of bikers seems unwilling to always heed the No Entry signs when felling is taking place, and there have on occasion even been conflicts.  Ospreys and other protected species are also a challenge for the timber industry, but recreation here is an increasingly significant income generator.
As a forest, Glentress seems to play the role of laboratory, trying different species mixes for CCF, but the constant incursion of Sitka makes it difficult to really achieve what they want to do. In the meantime, it is a great example of how forests are being  asked increasingly to fulfill diverse functions for society well beyond simple timber production.

Day 3 Carrifran Wildwood

The Wildwood project was started in 1993, a grass-roots community project to restore “native” woodlands  in the Southern uplands, as a demonstration of the kind of vegetation that was once found over most of southern Scotland. The 650ha site at Carrifran was purchased on Milenium Day, 01-01-2000. Regeneration would have been far too slow because of lack of seed source – in fact, as with Glentress, the main regeneration would be Sitka from neighbouring plantations, which requires constant weeding-out anyway! Over a half million trees have been planted since then, 75,000 by volunteers, and all the trees were grown by seed collected by volunteers and contracted to nurseries to grow on.
The choice of species was made after a site classification based on assessing what woodland type was likely to have been there in Neolithic times, which mainly upland birch-oak mix.
Our host for the day Philip Ashmole, one of the projects’ founders and author, with his wife Myrtle, of The Carrifran Wildwood Story (2009).IMG_4117
Philip explained that there was a deliberate decision made not to incorporate more southerly species that might subsequently move northwards in a warming climate; the range of elevations available at Carrfiran allow for a certain amount of migration for differing climates here anyway. But no attempt at building in either climate or disease resilience is being made through species choice- it is all about demonstrating what the lowlands of Scotland might have been like 6000 years ago before intensive farming, forest clearing and sheep grazing. The patchy plantings is also deliberate- there would always have been herbivores such as deer which would have prevented complete canopy closure, their numbers held in check by wolves and lynx which would have kept the herbivores moving.
A major expense has been a deer fence- “the best fence in Britain” paid for with lottery funding, which is hoped to last 10-20 years with maintenance. A group of mountain goats that had been living here were captured (bar three that could not be caught and were shot) and moved to the Windsor Forest park, ironically to aid in a peat conservation project by grazing regenerating trees and shrubs! This caused some conflict in the early days as the goats removal was fiercely opposed by another local group- a good example of conflicts than can arise between differing conservation goals.
80% of funding comes from private investors, there is also income from carbon credits, and the project has over 1000 subscribers.
Juniper in the foreground.
Little formal research is being undertaken at Carrfiran, deliberately so since research markers etc would interfere with the projects aim- to give visitors an experience of wilderness. However, despite being favourable to wolves and lynx in principle Philip disliked the word “rewilding” since it “has a lot of baggage associated with it”- though we did not hear what he was referring to.

One of the few original trees, a rowan, is visible on the bank behind Philip, now protected from grazers it has several seedlings growing around it.

Perhaps the main issue regarding resilience is that the project relies heavily on a small group of dedicated volunteers, but these are predominantly males over 60. A local hillwalking group regularly walk the entire fenceline to inspect it for faults.

A beautiful place and an inspiring project, well worth a visit.

Day 3: Eskdalemuir

For a complete contrast, our next stop was plantation forestry sites at Eskdalemuir characterized by single-age stands, hard edges and clear-fells. The forestry covers some 20,000 ha of mainly Sitka spruce established in the 1970s and 80s, grown on a 40-year rotation- much of it now ready for or just after felling and re-planting. The forestry is managed by a number of different forest management companies, and we were met by two forest investment fund mangers who discussed the project with us.

This site was the subject of a recent CONFOR report comparing incomes and carbon storage from forestry with upland sheep farming on similar areas, finding that while forestry only receives about 1/6th the subsidies of agriculture, before subsidies it can generate up to 3x the income, as well as being a net carbon store as opposed to an emitter of CO2 in the case of sheep farming.

Much of the discussion was about improving public relations regarding the impact of forestry of this nature. For the second rotation, regulations now stipulate greater age-structure diversity, softer edges with native species on the boundaries, much smaller areas of clear-fell. However, Sitka seems here to stay- in terms of productivity and profitability in difficult environments, it ticks all the boxes while few other species show any real promise. They certainly would not grow so fast-although given some of the limitations of timber quality resulting from the fast growth of Sitka this might not be a bad thing. However, for now the economics of upland forestry manged purely for profit seem to dictate no real increase in species diversification is likely- although worth in excess of  £100million, as only a small fraction of the investors’ total portfolio, the risks of catastrophic disease outbreak in Sitka seem to be something that will just be absorbed should the situation arise.

We were told that there has been next to no new conifer afforestation in the past few years, and that this is due to bureaucratic filibustering. Delays spawn further delays and the necessary permissions are just never signed off on. Broadleaf is ok, but while fracking licences for example are guaranteed to be granted within 16 weeks, applications for new conifer plantations have been sitting for several years without progress. This shows perhaps just how far public opinion has swung against conifer plantations, despite their profitability in recent years, which will have serious consequences for British forestry in the future which will meet a supply crunch by 2030 unless new afforestation occurs. In the meantime, with returns on investment forestry still very strong, our fund managers were looking to Ireland for new opportunities (though conifers are certainly not popular there either!).

Day 4 Galloway Forest Park


IMG_4152 Above- larch stand due for sanitation fellingIMG_4155

Examining the Forest Management Plans in the Clatterinshaws visitors’ centre.

Dumfries and Galloway is the biggest FC district in Scotland  covering 115000 ha with 20% of production at 700,000 cu m. The district generates £80m from timber and recieves £20m from the Scottish government for visitors centres and other recreational facilities.

The species make up consists of:

78% spruce

10% pine

8% broadleaf- this is expected to increase to help meet the national target of  20%

4% larch- all of which is scheduled for sanitation felling on account of Phytopthera ramorum which has been present since 2010. Some of the larch shows signs of healthy branches, and cuttings are being taken for grafting onto rootstocks in the hope of finding resistance- but “noone really expects to find any.”

Great spruce bark beetle has been present since the 1980s but so far can be controlled with one of the few successful biocontrol methods.

Afforestation at Clatteringshaws was begun in the 1940s, with most of these now felled and active felling underway for most of the 1970s plantations also. The area is now being managed to meet a range of production, environmental and landscape demands. New plantings include intimate species mixes to maximise soil benefits, such as shelterwood systems of beech, Silver fir and sycamore. A dozen conifer species and a dozen broadleaf species are in the plans. Rotation lengths for conifers are being extended. 60% of the plantation area is bog and in some cases on deep peat de-forestation is occurring, with the peatlands being restored after felling.

Public opinion was discussed: do the public understand forestry> A resounding “No!” was the answer given. Every two years, the FC commission a public opinion survey which makes for depressing reading (according to one of our lecturers) – forests are generally held in very negative regard, often associated with crime and vandalism. There is serious arson problems in forests closer to the big cities. On the other hand, around Clatteringshaws, while larch is generally preferred aesthetically for its more diverse herbaceous layers and understory, after an initial outcry when sanitation felling takes place (were it not for Phytopthera, most of the larch would be held onto for as long as possible), often the felling of the older blocks has opened up the views and improved opportunities for mountain biking and other activities, and generally been quite well received.

For further information on Scottish FC managment and planning see here.

Day 5 Slowing the Flow, Pickering

Last stop- another flood mitigation project, this time on a much larger landscape scale. The project was initiated after Pickering suffered severe flooding in 2007. The aim is to prevent chronic flooding up to a 1 in 25-year event. Slowing the Flow is a partnership project lead by Forest Research and with DEFRA as the main funder. The project is believed to have saved the town from the worst of the flooding in 2010.

Over a catchment of 66 square kms, there are 50 ha of woodland planted, 140 mini dams and a large bund protecting the railway. There are also mini-bunds and stockades made from spruce, and 170 large woody debris dams.

Although the media has focussed mainly on the soft landscaping measures of tree-planting etc, the engineered bund (see photos) is by far the most significant contribution. The key in flood mitigation is to reduce the peak- “slowing the flow”.

In terms of forestry, planning for species diversification is designed to meet climate scenarios for 2080, when 30% of the public estate is expected to become unsuitable for current species due to higher temperatures. 20% diversification is planned, including shag-bark hickory as a possible alternative to ash, grand fir, Macedonian pine and oriental spruce.

Beavers were discussed as being considered for introduction, with the proviso that they will simply be shot if they get out of hand: they will almost certainly undermine the railway through burrowing. There is roe deer and some red and muntjac, and our FC host, who advocated much more extensive re-planting of the moors which have suffered “centuries of abuse from grazing” commented “lynx would help.”


A great trip all considered, very informative and lots to think about. Now all there is to do is write the assignment… Many thanks to our lecturers Mark, James and Tim for organising everything and all the hosts who patiently answered all our questions.

I leave you with some atmospheric photos from where we stayed Thursday night, the beach at the funky and wonderful Boggle Hole hostel just below Whitby, the heart of Dracula country…





Into the New Wild

Book review: The New Wild: Why invasive species will be nature’s salvation by Fred Pearce

Icon Books 2015 new-wild

In 1910  New Zealand’s great botanist Leonard Cockayne described the dramatic change in  plant communities which had occurred since the first visit of Captain Cook to the country in 1769 (1). Some 560 new species from Europe, Africa and elsewhere had by become established by then, with half of them common throughout the country from the coasts to the highest mountains:

At first thought, the idea of 560 different sorts of plants- some of them the most aggressive weeds in Europe- having not only been loosed to do their will, but also having established a secure footing, would lead to the conclusion that, if not the flora of New Zealand, at any rate the primitive vegetation was doomed. No conclusion could be more incorrect. Were it not that man has changed, and is changing, the face of nature by means of his farming operations, his grazing animals, his fires, his drains, and his intensive exploitation of rain forest and flax swamp, the host of foreign plant invaders would be powerless- the indigenous plants, attuned to the special life conditions f their native land, would laugh these aliens to scorn. Why, even now, when the introduced plants have man as their potent ally, 66 percent of the species are rare or local, 40 percent being so rare as to be negligible, while merely 34 percent can be classed as extremely common, common, or fairly common, these being taken together. But these percentages do not emphasise the real state of affairs, for many of the commoner plants are confined to sides of toads, neglected building sites, and rubbish heaps- in short, to “waste ground” as it is called- and there are many other species restricted to cultivated land. In fact, probably only about 100 species are established on land where the vegetation would be exposed to modification only by grazing, fire, and other causes due to the indirect action of man.

The warfare, indeed, between the plant inhabitants of primitive New Zealand and the alien invaders is waged almost entirely under conditions where man takes a powerful hand, for, except for certain rock, stony debris, and water-plant formations, no primitive plant community has been desecrated by a single foreign invader. This is a very different version of the story from that even yet current in biological literature, where it is affirmed ad nauseum that the New Zealand vegetation is powerless when it comes into competition with the European plants, which by natural selection have become the very elite of the weed world.

Cockayne’s observations made over a hundred years ago are almost identical to those made forcefully in Fred Pearce’s provocative new book which takes to task invasion biology– the view that non-native species are generally “invasive”, constituting one of the greatest threats to biodiversity and ecosystem health, and need to be controlled and where possible eradicated completely- almost at any cost.

The European Commission on the Environment describe Alien Invasive Species (AILs) as “a major threat to native plants and animals in Europe, causing damage worth billions of euros to the European economy every year.” Bird Life International call for a far more extensive policy than that currently proposed, listing over 200 invasive species as of “high priority for urgent risk assessment” in addition to the 37 that are currently listed for control; while the WWF quote the World Conservation Union as saying

the impacts of alien invasive species are immense, insidious, and usually irreversible. They may be as damaging to native species and ecosystems on a global scale as the loss and degradation of habitats.

Hundreds of extinctions have been caused by invasive alien species. The ecological cost is the irretrievable loss of native species and ecosystems.

Pearce, winner the UK’s environment journalist of the year in 2001 and author of other books on climate change, population and sustainability, comprehensively rejects these assessments. Exactly as  Cockayne  describes above, “invasives” are more accurately thought of as opportunists which generally only move into ecosystems that have already been severely degraded by other human activities, and are able to thrive on our pollution where nothing else can. For example, the infamous Zebra mussels that spread through Lake Erie at such a rate in the 1980s were moving into an ecological desert so atrophied that everything else had already died- and apparently did a fairly good job of cleaning it up. In time, the previously endangered lake sturgeon, bass and migrating ducks moved back  to feed on the mussels.

This is a typical pattern with so-called “alien invasions” which are generally the consequence rather than cause of previous disturbance. Another infamous “invasive exotic”, Kudzu, from Japan- which became known as “the vine that ate the South” because of its rapacious spread through the southern US- had previously been widely planted as an ornamental, and for animal fodder and erosion control. It only got out of hand as a result of other land-use changes:

The vine hasn’t changed. It is still revered in Japan. What has changed in America is the land and people’s expectations of the land. Kudzu’s foliage is no longer needed to feed grazing farm animals, which now live in feedlots. The pastures are abandoned. No longer kept in check by grazing, kudzu now grows where it is not wanted, spreading unchecked almost anywhere south of the Mason–Dixon line. It is the enemy. The pastures are being turned into woodland, where kudzu is a problem.

The reality is that out of tens of thousands of introduced species- including most of our food plants and garden ornamentals- only a tiny minority ever become problematic or a threat to “native” vegetation in this way. Often, for all the trouble they cause, they also can do a lot of good; the costs they are claimed to incur are often wildly exaggerated based on simplistic extrapolations (2), and these could well be exceeded in some cases by the costs of control, which mainly are doomed to failure anyway. Nor is it true that they are generally likely to cause extinctions- Pearce concludes that this is based more of the assumption that  “exotics are bad” than supported by rigorous evidence. While there have certainly been cases of loss of biodiversity on remote islands, where local species have little options to extend their range, there are plenty of counter examples where introduced species have increased biodiversity. The problem is that “invaders” are simply not valued in the same way that “natives” are:

In fact we seem to have gone a long way from any interest in biodiversity. The interest is entirely to do with protecting natives and avoiding change.

…alien species don’t count and are not counted. They do not exist as part of nature. They have no place. They are un-nature, if not anti-nature. They should be gone. Under this definition, biodiversity in the 21st century can only go down. Extinction could cut the number of species, but introductions could never increase it. Thus the inconvenient fact that alien species actually increase real biodiversity in many places is simply defined away. Big Brother in Nineteen Eighty-four would be proud. Franz Kafka would be proud. Joseph Heller would have added an ecological chapter to Catch-22, if he had known. It sounded more like an ideology than good science.

A lot of the problem has to do with conflating “invasive” with “exotic/non-native”, but just as most “exotic” novel species are not invasive, so there are also “native invasives”. Bracken fern Pteridium aquilinum,  brambles Rubus fruticosus, and gorse Ulex europaeus,  all “native” to the UK but invasive as vigorous weeds or early colonisers of disturbed ground if they come across the right conditions.

More than that, and fundamentally to the whole debate, the line between what is considered “native” and “non-native” is not just blurry but scientifically meaningless. “Everything is visiting. Nothing is native” observes Pearce. What specific combination of plants have ended up living together in different areas at any given time is largely a function of chance. Some species made it across to Britain when there was a land bridge, some got stuck across the water when the sea levels rose again. In trying to maintain “native” vegetation we are necessarily picking a particular period in time from which to judge what can stay and what must go.

Rhododendron ponticum, a major target of conservation control in Britain because of its ability to prevent regeneration of woodland, had been “native” here before the last ice-age. Does this discount it on the basis that plant communities here have since evolved without it? The difficulty is that many other species are in the same category, but are not persecuted as invasive in the same way. Ken Thompson, author of another recent book on the same topic (2) points out that Fritillaria meleagris is generally considered a full-blooded British native, but was first recorded in the wild here only in 1736; while R. ponticum  first introduced to Britain in 1753, is still an “invasive exotic.” To further complicate matters, it is really a hybrid of three other Rhododendron species, which has evolved uniquely in the UK and is not found anywhere else! What, then, can it mean to call it anything but a native? Rhododendron  probably only became so widely spread anyway as a direct result of being extensively sown throughout British woodlands to provide cover for game.

(Conversely, Thompson gives the example of the quintessentially “English” oak  which,  having spent more than 99% of the last 2million years in Iberia, might more properly called Spanish.)

While there are specific cases of co-evolution between two species, they tend to be more exceptions than rules, and it is relatively rare for any group of species to be entirely dependent on their specific co-evolutionary companions- it turns out that ecosystems can usually function perfectly well, and often with increased diversity, with a mixture of old friends alongside new neighbours.  Pearce points out that Darwin did not see co-evolution as a principle driver of evolution, and quotes ecologist and invasion biology critic Mark Davis who states ‘nativeness is not a sign of evolutionary fitness’. Darwin was clear that the individual species is the primary unit of natural selection, not the “ecosystem”- a nebulous and controversial concept in itself. Much of the ideology surrounding the desire to keep nature in an idealized state of pristine “natural balance”, frozen at an arbitrary period of time (generally pre-Columbus) has less to do with Darwin than, as Daniel Botkin has argued, with the much older Judeo-Christian belief in the Great Chain of Being and guilt over the Fall from Eden (4).

Nature is always changing, and is proving in many respects far more resilient and adaptive than it is often portrayed. While most conservation efforts focus on extermination of plants that happen to make it onto the “invasive species” lists,  entire new ecosystems, and often highly diverse regenerating secondary forests are emerging all around us.  Perversely, such habitats are not deemed worthy of conservationists’ efforts to protect them- despite increasing evidence that even most so-called “pristine” habitats were subject to significant anthropogenic change in pre-history (5). Pearce sees this as a blinkered and narrow view and a sad lost opportunity. It is this “New Wild” that he feels we should now turn our attention to, since in the rapidly changing world of the Anthropocene,  there is very little, if any, “pristine” wild left. With more ecologists like Davis speaking out from this perspective of a “new ecology”(6), science has already moved on to a large degree from earlier conceptions of ecosystem balance. Now it is time for public understanding of this science, and conservation policy, to catch up.

Pearce has written an engaging book that should be a valuable contribution to this often confusing debate. If he falls short in any area, it is perhaps the cursory passing over of the threat posed by novel pathogens, which are increasing due to global trade of plant material with potentially devastating consequences to trees and shrubs (7).  In general though he is careful not to fall into the trap of claiming there is no issue at all with introducing new species which might be at the very least weedy or have unintended consequences. Some newcomers can cause serious problems, more for humans than for “nature” though,and noone wants rampant weeds in their gardens. Plants should be investigated on a case-by-case basis, not assumed to be inherently bad or noxious on the basis of the largely spurious notion of nativeness: the vast majority are benign. This raises another issue, as pointed out by Thompson: the public’s goodwill, without which even the most favourable eradication or control efforts cannot in any case succeed. The public do not intuitively divide plants into native or non-native, but assess them on their characteristics of usefulness or aesthetics, which is exactly why plants are frequently assumed to have been native for a long time when, like the fritillary they are relative recent arrivals, and vice-a-versa. It is not just environmental issues at stake here, but the public’s trust in the integrity of science.

More than just a critique of conservation, Pearce also presents a damning indictment of science. With honorable exceptions, few scientists have spoken up against the tendency of NGOs and policy makers to rely heavily on just one or two studies which have either been misrepresented or have little real evidence to back them up, and costly and often damaging alien eradication programs have been allowed to continue unnecessarily, often for decades. As is clear from Cockayne’s book written at the beginning of the last century, there was never any very solid science behind invasion biology, and it is time for this to be more widely understood and debated in the public realm.


  1. Cockayne, L.  1910 New Zealand Plants and their Story
  2. see Pimentel, D. et al 2000 Agriculture, Ecosystems and Environment 84 (2001) 1–20
    Economic and environmental threats of alien plant,
    animal, and microbe invasions Agriculture, Ecosystems and Environment 84 (2001) 1–20.  Pearce claims the widely cited figure of $1.4 trillion being the annual coast to the global economy from invasive species is an extrapolation to the entire world from just six major economies, and the biggest three causes of these costs coming from rats, weeds and plant pathogens in agriculture; among other problems Pearce points out,  no accounting is allowed for possible benefits to the economy from aliens (such as cleaning water pollution in the Lake Erie by the Zebra mussel mentioned above).
  3. Thompson, K. Where do Camels Belong?
  4. Botkin, D. The Moon in the Nautilus Shell
  5. Bowman, David MJS, et al. “The human dimension of fire regimes on Earth.” Journal of biogeography 38.12 (2011): 2223-2236.
  6. see for example Brown, J. and Sax, D. An Essay on Some Topics Concerning Invasive Species Austral Ecology (2004) 29 , 530–536:

    The rare, restricted species are disappearing and the common widespread species are becoming even more abundant and widely dispersed. This hasbeen referred to as the homogenization or cosmopolitanization of the world’s biota (Brown 1995; McKinney & Lockwood 1999).Is this decrease in global biodiversity a bad thing? Is the net increase in local species richness due to invasions a good thing? Is high species richness desirable? We do not believe that these are scientific questions.Science can elucidate the causes and consequences of these changes in biodiversity, but ultimately deciding what is good or bad is a moral and social issue. Few people would question whether the dozens of exotic flower and vegetable species in their gardens are desirable. The value judgements may change, however, if some of those same species were to become naturalized and spread into wild areas or to become serious weeds in agricultural fields.

  7. Rackham, O. 2014 The Ash Tree Little Toller Books, Dorset