Breaking the (Polymer) Chain: Eliminating Plastic Tree Shelters from NHS Forest Planting Schemes
Low-plastic tree planting is something we have been looking at closely for some time. There are a number of ways plastic can creep into the process, but the main source is tree shelters. While ubiquitous today, plastic tree shelters are a relatively recent product first developed in the late 1970s for commercial forestry applications. Shelters can be an effective tool that favourably influences planting outcomes. Unfortunately, post-establishment removal and disposal is commonly overlooked with the result that plastic waste is left in the natural environment.
Trees are evidently able to take root without human interventions as they have done on their own initiative for millions of years. In addition, growing awareness of the ecological impact of microplastics has increased the level of scrutiny given to routine use of shelters. However, in recent years an increasing number of sustainable, non-plastic shelters have become available, and there are legitimate reasons for using such products where this facilitates the establishment of trees.
In this blog we consider NHS Forest’s own use of tree shelters and outline what we have been doing to reduce the plastic footprint associated with our tree planting work.
What exactly do we mean by a ‘tree shelter’?
A tree shelter is any kind of physical barrier that protects young trees and can take many forms, from elaborate cages manufactured from metal or wood through to simple shoot protectors fitted to the terminal leaders (topmost stems) of whips (young trees). The focus of this blog will be the most common variants seen in the UK: linear tubes fitted around individual trees and secured with a stake or bamboo cane.
Why does NHS Forest use tree shelters anyway?
Use of tree shelters demonstrably improves planting outcomes, both in terms of survival rates and the condition and form of the trees during the establishment phase. A 2021 study published in the journal Science of The Total Environment showed that shelters increased establishment rates by 70% on average, with 85% of sheltered trees surviving to maturity vs. just 50% of unsheltered trees.
We understand that healthcare sites often invest considerable time and energy into planting and maintaining the trees they receive from NHS Forest. As a result, we are keen to see as many of our trees as possible survive to maturity in the broadest possible range of circumstances.
What are the benefits of using tree shelters?
First and foremost tree shelters are intended to protect against damage by mammals that frequently browse foliage and strip the bark of unprotected trees. Deer and rabbits may be less prevalent in built up areas, but shelters are also effective in deterring gnawing by rodents such as squirrels, mice and voles that can stunt growth or even kill trees outright.
There are also a number of benefits linked to maintaining the trees. Shelters increase the visibility of planted areas, helping to avoid accidental damage from mowing or strimming and easing routine inspection and weed control. In addition, shelters encourage linear growth during early establishment and can protect trees against inadvertent exposure to spot herbicides if spraying is undertaken.
Shelters also shield trees against inclement weather, acting as a windbreak and reducing exposure to frost. Translucent products function as miniature greenhouses, creating a microclimate around the young tree, and trapping moisture and warmth to stimulate healthy growth.
What are the environmental issues associated with plastic tree shelters?
Tree planting is a positive step for the environment with tangible long-term benefits that outweigh the associated negative externalities. The manufacture of tree shelters does result in carbon emissions, with a single polypropylene tree shelter accounting for around 440 grams of carbon (linked to production and processing of raw materials). Yet this would be offset many times over by the trees themselves, which have the potential to sequester far greater quantities of carbon over their lifetimes.
Much more criticism has focused on the issue of plastic waste. Tubes and spirals are not designed to be left indefinitely but installed for a few years (until outgrown by the tree) and then removed for disposal. Many responsible planters are proactive in collecting tree shelters, but the long-term nature of tree establishment means this is sometimes overlooked and shelters remain in situ, littering the countryside with plastic waste and harming wildlife. Government woodland creation grants typically stipulate that tree protection must be removed after 10 to 15 years. However, there is no obligation or additional provision for the shelters to be recycled or disposed in a sustainable manner.
A further issue has been difficulty recycling tree shelters at the end of their functional life. Exposure to the elements leaves plastic tubes degraded and brittle, and frequently contaminated with soil and plant material. As such, tree tubes are often rejected for processing by waste management companies and local authorities. While shelters can be – and are – recycled, manufacturer operated schemes are reliant on user engagement and account for only a fraction of the output of new shelters. Low-plastic tree planting is a far better strategy.
What has NHS Forest been doing to promote low-plastic tree planting?
NHS Forest has adopted a proactive approach to reducing our use of plastic tree shelters since 2019, and not supplied any ‘traditional’ tubes or spirals manufactured from PVC, polypropylene or other petrochemically derived materials since 2022. During the 2023-24 planting season our tree bundles were supplied with bio spirals manufactured from non-toxic and biodegradable plant starch.
Bio spirals should be removed after a few years of growth and can be processed as biowaste for disposal in an industrial composting unit, wherein they will fully degrade within six months. It is important to note, although bio spirals will also biodegrade over time if left in the environment, they may take many years to fully break down. NHS Forest strongly encourages removal and disposal of shelters be included as part of the management plan for any trees being planted.
What are the current alternatives to plastic shelters?
Low-plastic tree planting is easier than ever. A multitude of new non-plastic shelters have come to market in recent years, including products manufactured from (in no particular order):
- Plant starch – including the bio spirals currently supplied by NHS Forest
- Wood fibre
- Cardboard
- Wool
- Organic cotton
- Sugar waste
Product trials are at an early stage and no single product has yet been established as the preeminent replacement for the most common types of plastic shelters. We are currently exploring opportunities to trial other products as part of our tree bundle orders for the 2024-25 season. More information will be published on the NHS Forest website as soon as the details has been finalised.
Why not just plant trees without shelters?
Not using shelters is without doubt the tree planting option with the lowest environmental impact.
However, tree planting is done with a goal of establishing a tree in a specific location and with a specific purpose. Given the timescales and costs involved it is pragmatic to want to maximise the likelihood of successful establishment and mitigate against factors that may adversely impact the planted trees.
There will be situations where shelters are redundant, or at least inessential. This is particularly the case in urban locations with limited wildlife or areas enclosed by buildings or fencing. Conversely, there will be other instances where the use of shelters is the only practicable option to enable the trees to reach maturity.
But there is an opportunity cost associated with stock use, and where young trees are lost due to avoidable mammal damage or because the trees were not discernible for maintenance, this precludes an opportunity for successful tree planting elsewhere. The use of tree shelters may make all the difference between successful establishment and failure.
Can NHS Forest supply my trees without shelters?
Yes, we can exclude shelters from any order on request and accept that applicants will have a much better sense of whether or not they are necessary for their site – although we may request some clarification in relation to your application and plans for how the trees will be maintained.
We would recommend an abundance of caution when considering the need for shelters and advise recipients to give serious consideration as to the potential for unprotected trees to come to harm during the first few years in the ground. Trees are generally less than one metre high as supplied, so planters should consider how they will delineate the trees for maintenance. An apparent absence of browsing mammals during working hours does not rule out sporadic or nocturnal visitors to the site and new tree planting may draw in wildlife from the surrounding area.
Will your approach to supply of shelters change in the future?
Supplying orders with non-plastic shelters will remain the default for NHS Forest tree orders for the time being. In our experience this ensures recipients will see a much better establishment rate. This will set planters of all abilities up for success in creating and developing green spaces for health. It will also provide a better return on the time and costs associated with supplying and planting the trees.
We will continue to review our approach to low-plastic tree planting with a focus on operating in line with best practice for both the planted trees and the wider environment.
Thanks for reading to the end
While you’re thinking about trees, why not head over to our planting pages and apply for fully funded trees for your healthcare site – with or without tree shelters.