A review of challenges and future pathways for decision making with treeshelters - A German and European perspective

Abstract

Since the invention of treeshelters in Europe during the late 1970s new views on them have emerged. We identify critical challenges and propose new pathways towards a 'plastic-reduction strategy in forestry' by analysing available products on the European market, by raising questions on legal aspects at the end of their service life and by considering case studies of German plantations, calculating their costs with respect to subsidies. We point to new tools for complex decision-making with treeshelters and fencing as two selected protective measures. Our findings show that on the European market, there are 161 different types of treeshelters available. There are five groups of material types ranging from polypropylene and compostable plastics to shelters made from wood, paper or jute. As for most material types, there is not certification for biodegradation under outdoor temperate forest conditions. However, a recent survey from Germany reveals that collecting activities are insufficient and not in line with the laws for forestry, nature protection or the circular economy. An analysis of state subsidies for treeshelters show that in Germany oak plantations up to 85% of the total costs are subsidised. Moreover, the costs of removal have been integrated insufficiently and there are no provisions that force forest owners to remove materials after they have been used. A comprehensive strategy for European forestry should also consider innovation of new treeshelters that are made from fully bio-based material, are fully biodegradable under forest conditions, function as classical shelters and show better performance in life-cycle assessments. ARTICLE HISTORY

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A review of challenges and future pathways for
decision making with treeshelters – A German and
European perspective
Yannic Graf, Sebastian Hein & Anton Sebastian Schnabl
To cite this article: Yannic Graf, Sebastian Hein & Anton Sebastian Schnabl (2022): A review of
challenges and future pathways for decision making with treeshelters – A German and European
perspective, Journal of Forest Research, DOI: 10.1080/13416979.2022.2029281
To link to this article: https://doi.org/10.1080/13416979.2022.2029281
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REVIEW
A review of challenges and future pathways for decision making with
treeshelters – A German and European perspective
Yannic Graf
a
, Sebastian Hein
b
and Anton Sebastian Schnabl
a
a
Research Associate, Department of Siviculture, Forest Growth and Yield, University of Applied Forest Sciences Rottenburg Rottenburg A. N;
b
Professor, Department of Silviculture, Forest Growth and Yield University of Applied Forest Sciences Rottenburg Rottenburg A. N
ABSTRACT
Since the invention of treeshelters in Europe during the late 1970s new views on them have emerged.
We identify critical challenges and propose new pathways towards a ‘plastic-reduction strategy in
forestry’ by analysing available products on the European market, by raising questions on legal
aspects at the end of their service life and by considering case studies of German plantations,
calculating their costs with respect to subsidies. We point to new tools for complex decision-
making with treeshelters and fencing as two selected protective measures. Our ndings show that
on the European market, there are 161 dierent types of treeshelters available. There are ve groups
of material types ranging from polypropylene and compostable plastics to shelters made from wood,
paper or jute. As for most material types, there is not certication for biodegradation under outdoor
temperate forest conditions. However, a recent survey from Germany reveals that collecting activities
are insucient and not in line with the laws for forestry, nature protection or the circular economy. An
analysis of state subsidies for treeshelters show that in Germany oak plantations up to 85% of the
total costs are subsidised. Moreover, the costs of removal have been integrated insuciently and
there are no provisions that force forest owners to remove materials after they have been used.
A comprehensive strategy for European forestry should also consider innovation of new treeshelters
that are made from fully bio-based material, are fully biodegradable under forest conditions, function
as classical shelters and show better performance in life-cycle assessments.
ARTICLE HISTORY
Received 5 October 2021
Accepted 11 January 2022
KEYWORDS
Treeshelter; market analysis;
circular economy act; forest
act; proper and sustainable
forest management
Introduction
The first types of treeshelters or treeguards were developed in
1979 by Graham Tuley (England) for use in open landscapes
(Tuley 1983, 1985). Since then, they have become very wide-
spread in European forestry (e.g. Dubois et al. 2000; Famiani
et al. 2007; Gautier et al. 2007; Hein and Spangenberg 2012)
and also worldwide (e.g. Urretavizcaya and Defossé 2013;
Defaa et al. 2015). Today, in Europe, this type of individual
protection of young trees mostly consists of transparent,
stable, closed-walled (so-called unventilated) or open-
walled (so-called ventilated) hollow-chamber walls made of
plastic materials (Figure 1). Treeguards are made of meshes,
with an open matrix of up to 1.5 cm grid width made of
plastic strings glued together in squares (Figure 2). Both
forms (here simply referred to as treeshelters) are either
resistant to ultraviolet (UV) radiation in outdoor conditions
and must therefore be removed manually (Hein et al. 2014,
2021b) or are expected to decompose without leaving resi-
dues (Arnold and Alson 2012; Hein et al. 2014; Hein and
Graf 2019).
The technical development of treeshelters was triggered
by numerous expectations from a European forestry perspec-
tive. Originally, treeshelters were supposed to both provide
protection against herbicides in agriculture, agroforestry,
landscaping and horticulture, and protect trees from brows-
ing or fraying by animals, game or small rodents (McAdam
1991; Potter 1991; Kerr 1992). In addition, treeshelters are
thought to improve the visibility of plants during tending
operations, to reduce losses during activities of crop estab-
lishment, to reduce the risk of late frost, to allow the use of
smaller planting assortments for reduced costs or to speed up
tree height development, thereby shortening the mainte-
nance time during crop establishment (Tuley 1983; Kerr
1992). Costly protection of the whole planting area by
using large fences should also be reduced (Köckritz and
Ammer 2009; Helfenstein et al. 2017). In some cases, tree-
shelters have also been used to reduce the need for mechan-
ical weeding and tending against competing vegetation
(Löffler et al. 2012).
Many of these expectations have been met success-
fully on numerous deciduous or coniferous tree species
grown in Europe (deciduous: Acer pseudoplatanus,
Castanea sativa, Juglans nigra, Olea europaea, Prunus
avium, Quercus coccifera, Quercus rubra, Quercus pet-
raea, Quercus robur, Quercus suber, Quercus ilex and
Robinia pseudoacacia; coniferous: Larix spp., Pinus hale-
pensis, Pinus nigra, Pinus pinaster, Pinus silvestris, Picea
abies and Pseudotsuga menziesii) (McAdam 1991; Kerr
1992; Bergez and Dupraz 2000; Bellot et al. 2002;
Jiménez et al. 2005; Famiani et al. 2007; Gautier et al.
2007; Oliet and Jacobs 2007; Padilla et al. 2011; Castro
et al. 2014; Ceacero et al. 2014; Petersen 2016).
Therefore, treeshelters play an important role in today’s
forestry management in Europe. For the European market,
however, only a few insights into current production or
sales figures are available. Recent surveys and projections
(Hein et al. 2019) estimate that for Germany, there are
millions of annual new plantings. In addition, due to the
still unresolved forest–wildlife conflict, a further increase
in sales is to be expected.
CONTACT Yannic Graf graf@hs-rottenburg.de Research Associate University of Applied Forest Sciences Rottenburg D-72108 Rottenburg A. N
JOURNAL OF FOREST RESEARCH
https://doi.org/10.1080/13416979.2022.2029281
© 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/),
which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.

Background
Treeshelters are currently mostly made of plastic materi-
als. For several years, there has been public criticism of
plastic because it is increasingly and mostly uncontrollably
released into the environment and can pose a threat to
a wide variety of living organisms (e.g. Thompson et al.
2009; Cole et al. 2011; Huerta et al. 2016; Li et al. 2016; De
Souza et al. 2018). It also shows a high persistence in the
environment. In recent political developments, this has led
to the adoption of the EU Plastic Reduction Directive
(Directive (EU) 2019), thus requiring member states to
exclude products made of oxo-degradable plastic from
the markets (ban on placing on the market). The outcome
has been new legal frameworks for the European market of
treeshelters – for example, the necessity to remove specific
shelter types – which now have to be discussed.
The use of treeshelters is also associated with high
labour costs during installation, including costs for buying
the shelters themselves and later labour costs for removal
and disposal. Furthermore, when protecting a cultivated
area against browsing by game, a complex decision has to
be made on whether it is preferable to build a fence (i.e.
protection of the whole area) or to use individual protec-
tion (i.e. individual trees by treeshelters). The multitude of
influencing factors in this econometric question may often
lead to wrong decisions, which are not satisfying from
other viewpoints like forest aesthetics or forest planning.
Again, solutions need to be found in the decision-making
process for the optimal use of treeshelters per hectare
versus fencing. This also should include state subsidies
for treeshelters, among other considerations.
In the following sections, therefore, important current
aspects for Europe concerning the use of treeshelters are
reviewed. Based upon new publications and our own
research, specific information from the situation in the
Federal Republic of Germany is discussed as an exemplary
explanation of the European situation. Thereby, besides phy-
siological research on treeshelters, in this review 1) the cur-
rent market situation of treeshelters and 2) the recent legal
situation concerning the removal of plastic materials from
the forest are integrated, and 3) the economic situation of the
use of treeshelters in forest estates is considered from
a European perspective and as a case study from a German
perspective.
Physiological eects of treeshelters
The benefits of treeshelters mentioned above led to several
early, important ecophysiological investigations in Europe
on the growth and physiology of young trees. The microcli-
matic environment of the seedlings inside treeshelters is
significantly altered in terms of light conditions, tempera-
ture, CO
2
and humidity: photosynthetically active radiation
is reduced by about 20%–70%/ Ø 60% depending on expo-
sure, exposition in the landscape, colour and transparency of
the type of shelter (Bergez and Dupraz 2009; De Castro et al.
2014). Closed-walled treeshelters increase daily temperature
and humidity inside the tube and limit CO
2
availability,
Figure 1. Transparent, stable, ventilated, hollow-chambered treeshelters
(Source: Schnabl)
Figure 2. Meshes with an open matrix of up to 1.5 cm grid width made of
plastic strings glued together (Source: Schnabl).
2Y. GRAF ET AL.

thereby reducing transpiration, the photosynthetic rate and
thus biomass accumulation of seedlings due to insufficient
air exchange between inside and outside conditions (Bergez
and Dupraz 2000, 2009). Such an environment promotes
height growth but reduces diameter growth (Abe 2021;
Bergez and Dupraz 2009), leading to some lability of the
plants. The lack of mechanical stress on the young plants
due to wind protection inside the treeshelter and due to the
shelter walls as a lateral support is an additional influencing
factor on the reduced diameter growth and the deteriorated
shoot-root ratio (Coutand et al. 2008). Improved biomass
production and increased height growth have been observed
in aerated (ventilated) compared with unaerated (unventi-
lated) treeshelters (Bergez and Dupraz 2000). Beyond tem-
perate climatic conditions, these relationships have also been
confirmed for Mediterranean and semi-arid natural environ-
ments (e.g. Bellot et al. 2002; Chaar et al. 2008; Padilla et al.
2011). Therefore, these ecophysiological observations are
now considered valid across a wide geographical gradient
for the most relevant growing conditions from northern to
southern Europe. However, as the findings are currently not
questioned, there is currently no significant research on these
aspects in Europe or specifically in Germany.
Market situation of treeshelters
The European market of treeshelters was estimated to be
worth €100 million per year in 2007 (Jones 2007). There are
currently no valid numbers of the European market for
the year 2021. Furthermore, there are no detailed figures for
individual European countries available. In Germany, a recent
survey was done in a single state (Hein et al. 2019) and then
upscaled to the country level; it estimated 11 million newly
installed treeshelters per year in the whole country. Because of
recent reflections of the authors in the context of climate
change (due to the use of rare drought-tolerant but also
more palatable tree species), this number is expected to rise.
On the other hand, a significant decrease seems also to be
likely because of the most recent trend to reject plastic-based
products in modern forestry. However, there is currently not
a more precise projection of the real dynamics for Germany
and even less so for Europe as a whole.
Furthermore, a survey on the types of treeshelters avail-
able in Europe has been conducted from June to
October 2018 (Hein and Graf 2019) using country-specific
sales catalogues of forestry trading companies or Internet
queries in the case that producers have set up their own
sales and vending organisation. Interestingly there is a clear
picture on the various types and brands of treeshelters avail-
able on the European market: according to the authors, 161
different types of treeshelters made of plastic, wood, paper or
jute are commercially available in Europe. From the product
descriptions, the areas of forestry, viticulture, orcharding and
landscaping as well as a “universal application area” can be
identified. Fifty-eight different treeshelters are for the for-
estry application area only. Seventy-three products are exclu-
sively recommended for the application areas of viticulture,
orcharding and landscaping, and 30 different shelter types
are shown without special allocation (cf. above “universal
application area”). Thus, forestry is an important sales mar-
ket for the treeshelter industry.
The different lengths offered for each type of tree-
shelter are not included in the previously mentioned
figure. While universal treeshelters are offered in almost
all length classes (Figure 3), clear trends are emerging
for forestry and viticulture, orcharding and landscaping
applications. In forestry, length classes are needed for
protection against row (Capreolus capreolus) and red
deer (Cervus elaphus) and are therefore mainly offered
with a focus on the 120–180 cm length range. Lengths
shorter than 120 cm are rarely used in forestry – against
hares (Lepus europaeus) and rabbits (Oryctolagus cuni-
culus), nevertheless still available on the market. For
viticulture, it can be assumed that young grapevines
are more in need of protection against browsing by
small animals for a shorter period of time; therefore,
protection is merely needed for 1–3 years, and an
emphasis is given on the 40–60 cm length range in the
sales catalogues.
There is also a new view on the market regarding the
types of materials used to produce treeshelters available
in Europe. From the perspective of also reducing plastics
in a forest environment, five different materials for man-
ufacturing treeshelters were identified (Hein and Graf
2019) (Figure 4):
Treeshelters made of regular petrochemical plastics
(material type 1) dominate the market, with a 65% share as
recorded from the sales catalogues or product descriptions
provided by the producers. Assuming that the materials used
in the group of material type 5 are similar to material type 1,
an additional 21% of the market uses regular petrochemical
plastics. Six per cent of the treeshelters are made of
Figure 3. Number of treeshelters on the market by length class and application area.
JOURNAL OF FOREST RESEARCH 3

compostable materials certified and labelled after DIN EN
13432: (2000) (material type 3) and 5% are made of wood,
paper or jute (material type 4). In 2018, treeshelters made
from material type 2 (now banned, see below) had a share
of 3%.
Even if no regional or national statistics are available on
tree species protected by treeshelters, mainly 1) rare, 2) slow-
growing and 3) tree species that are at risk of browsing
(palatable) and fraying need treeshelters as protective mea-
sures. In Germany, but also in Europe, these are mainly
deciduous trees (e.g. Quercus spp., Acer spp.) and, among
the coniferous tree species, mainly the silver fir (Abies alba).
Many other tree species are also protected, but less as protec-
tion against browsing than as protection against fraying –
which is gnawing off pieces of bark (in winter) or pulling off
entire strips of bark (in summer) primarily by red deer (e.g.
P. menziesii, Larix spp.). Picea or Pinus species are usually
hardly or even not at all protected due of their low risk of
browsing by row deer, red deer or hares and rabbits.
Interestingly, the necessity for protection of some tree spe-
cies with treeshelters is questioned by some scientists
(Petersen 2016; Hein et al. 2019) because of economic con-
siderations (high costs vs short time of protection), even
though trees are protected quite often in practical forestry.
Legal aspects on removal – A case study from
Germany
Treeshelters are an important tool in forestry. They are
designed to stay at least 5 years in forest outdoor conditions
before they have fully fulfilled their purpose. Later, they are
to be removed, collected and potentially re-used or dumped
as waste according to legal regulations or economic interests
of the circular economy and its respective acts. However,
recently the adoption of the EU Plastic Reduction Directive
(Directive (EU) 2019) has also been a ‘game-changer’ with
respect to treeshelters, as European Union member states
now have to exclude products made of oxo-degradable
plastics from the markets. This new European rule is
now about to be integrated into the various legal frame-
works of the individual countries in Europe. Thus, an
immediate impact is expected to happen quickly with
respect to the material types mentioned above: treeshelters
of material type 2 are no longer allowed on the market.
They have been removed from the market and are thus no
longer available for sale.
A recent analysis for Germany of the legal situation of
treeshelters in forests after they have fulfilled their protec-
tive purpose (Hein et al. 2021a,b) concluded that “non-
removal” does not conform at all with the laws in force.
We evaluated the legislation with a specific focus on the
question “What to do with plastic-based treeshelters after
the end of their service life?” in the context of the close-to-
nature forest management system in Germany. In detail,
we analysed the following legal framework: the German
Federal Circular Economy Act, the German Federal Soil
Protection Act, the German Federal Bio-Waste Ordinance,
the German Federal Forest Act and Nature Conservation
Act as well as the corresponding legislation at the state
level of two of the 16 German states – one located in the
north-west of the country one located in the south-west.
Particularly, the Circular Economy Act (Hein et al. 2021a)
requires treeshelters from groups 1, 2, 4 and 5 to be
removed. If shelters of material group 4 are potentially
impregnated with toxic compounds to ensure a sufficient
service life, removal is required. Only treeshelters from
group 3 can potentially be left at the site of installation,
if they are reduced to small pieces, which in turn are mixed
with topsoil and fully degrade in forest conditions.
However, even for such a practice a specific permit needs
to be granted from the authority responsible for the cir-
cular economy in consent with the forest authority. Thus
summarising, the current practice of leaving treeshelters
on site or just hesitant removal and restrained disposal
Figure 4. European market supply of types of treeshelters by material type (all sectors of forestry, viticulture, orcharding and landscaping as well as a ‘universal
application area’), N = 161. Material Type 1: regular petrochemical plastics; Material Type 2: oxo-degradable plastics; Material Type 3: compostable plastics
(certified after DIN EN 13432:2000-12 (2000)); Material Type 4: wood, paper or jute; Material Type 5: no material information available.
4Y. GRAF ET AL.

after having fulfilled their purpose clearly contradicts legal
provisions in Germany. It is expected that similar contra-
dictions between legal specifications and actual removal
also exist and are part of the frequent practice in other
European countries. Unfortunately, similar studies are not
yet available for other countries in Europe.
A recent survey on treeshelters after their service life
showed a major challenge for German forest management,
but also likely valid for the broader European situation (Hein
et al. 2019). According to our questionnaire among different
categories of forest estates in the State of Baden-
Württemberg (i.e. Black Forest region), public forest owners
responded that considering the last 20 years, 49% of the used
treeshelters have been removed. Among large-scale privately
owned forests with a size of > 1,000 ha, the rate of removals
was much lower, only 20%. This is even more problematic
because many forest owners were not able to tell the exact
number of treeshelters installed in their estates nor were they
able to tell the material type. This is also surprising when
considering the strict specifications of close-to-nature and
sustainable forest management in Germany and its environ-
mentally friendly forestry legislation.
Costs and state subsidies – A case study from
Germany
The use of treeshelters is associated with a wide range of
costs. For an estimation of the per-hectare costs in
Germany, Graf et al. (2021a,b) set up two case studies
to start a more comprehensive discussion on the pgros
and cons of treeshelters, including subsidies from the
states, the country and the European Union (Table 1).
The following two silvicultural cases were used: 1)
a group-wise planting with oaks and 2) a whole-area
planting (also oaks). Until a new forest is fully secured
against early risks of mortality, the costs for preparing the
planting area; the costs for procuring young seedlings; the
labour costs for planting and installing treeshelters, rods
and ties; and the costs for protecting the plantation
against competing vegetation and wild animals have to
be calculated. The basis for calculation of the total costs
were: for the group-wise plantation 70 groups/ha of 25
oaks. The following were also considered: costs for the
preparation work of the planting area (1 × 15 h/ha at
€40/h); costs for the plants (€1/oak VAT); costs for plant-
ing (40 oaks/h and labour cost of €40/h); costs for tree-
shelters including rods, installation and labour (€3.20/
treeshelter); costs for fencing with mesh and posts includ-
ing labour (€7/running meters[rm]); and costs for weed-
ing and tending until full stand establishment (2 × 25 h/
ha at €40/h). The costs for removal were considered
separately and are integrated in a second step. They
consist of personnel costs (€40/h) and were set to €0.80/
treeshelter and for fences €3/rm according to current
forestry conditions in Germany (Hein et al. 2014). The
exact costs for the removal of treeshelters can vary up to
€2.00/treeshelter depending on individual circumstances
(competing vegetation, slope gradients, weather condi-
tions etc.).For this purpose, federal states were selected
as examples and the costs per hectare as well as subsidies
per hectare based on their current state guidelines on
subsidies were determined.
For average forest conditions in Germany, a total of
€11,700/ha can be estimated for such a group-wise plantation
with oaks (Table 1). Of this, almost 50% is spent on individual
protection (treeshelters). In the case of a whole-area oak plan-
tation (Table 2), the costs amount to a total of €21,700/ha,
almost double the amount of a group-wise plantation. In this
case, the costs for the fencing, including its later removal,
represent 14.5% of the total.
Forest renewal is a general social desire, so a plantation is
also worthy of support by state funding. There are very
different funding schemes in the 16 federal states of
Germany. These subsidies can refer to the purchase of new
plants but also to the purchase and installation of treeshelters
or the building of fences. As an example of the federal states,
Baden-Wuerttemberg and Schleswig-Holstein have been
compared for silvicultural case 1 (Table 1) and
Brandenburg and Saxony-Anhalt have been compared for
silvicultural case 2 (Table 2). Schleswig-Holstein provides
a 85.0% subsidy in the case of oak group planting. In Baden-
Württemberg, the subsidy is 61.7%. (in each case without the
removal of protective mechanisms). In the case of whole-area
oak plantations protected by fencing, the subsidies in
Table 1. Case study ‘plantation of oaks in groups using treeshelters.
Operation Calculation Basis
Costs
€/ha
Subsidies
€/ha
Baden-
Wurttemberg
Subsidies
€/ha
Schleswig-
Holstein
Preparing
planting area
1 x 15 h/ha (€40/
h)
600 2,800 510
Plants 70 Groups of 25
oaks (€1/oak)
1,750 1,487.5
Planting 1,750 oaks; 40
oaks/h (€40/h)
1,750 1,487.5
Treeshelter, Rod
& Installation
1,750 oaks
(€3.20/
treeshelter)
5,600 2,975 4,760
Weeding
& Tending
2 x 25 h/ha (€40/
h)
2,000 1,440 1,700
Sum €11,700 €7,215 €9,945
Aim of regeneration – 80% oak’, with two selected states: Baden-Wurttemberg
and Schleswig-Holstein. Each treeshelter is assumed to cost €3.20 (€1.50 for
the material, €0.70 for the rod and €1.00 for the setup). Costs are compared
with and without grants and without removal of the treeshelters. The basis of
the calculation is grant schemes of the federal states as of December 2020,
without VAT.
Table 2. Case study ‘plantation of oaks in rows using fencing.
Operation Calculation Basis
Costs
€/ha
Subsidies
€/ha
Brandenburg
Subsidies
€/ha
Saxony-
Anhalt
Preparing
planting area
1 x 15 h/ha (€40/h) 600 600 510
Plants 8,000 oaks (€1/oak) 8,000 4,000 6,800
Planting 8,000 oaks; 40 oaks/
h (€40/h)
8,000 2,400 6,800
Fencing incl.
Installation
450 rm
(€7/rm)
3,150 2,250 2,475
Weeding
& Tending
2 x 25 h/ha (€40/h) 2,000 800 1,700
Sum €21,750 €10,050 €18,285
Aim of regeneration – 80% oak’, with two selected states: Brandenburg and
Saxony-Anhalt. Costs are compared with and without grants and without
removal of fencing. The basis of the calculation is grant schemes of the
federal states as of December 2020, without VAT.
JOURNAL OF FOREST RESEARCH 5

Brandenburg case study are 46.2% and the subsidies in
Saxony-Anhalt are 84.1% (each case without removing the
fencing).
In the first step, the fictitious case study on costs and
state subsidies deliberately considers only the procure-
ment costs of the treeshelters with their rods. It does not
include the costs for removal at the end of the intended
use. However, removal has to be included and could be
priced at approximately €0.80 per treeshelter, as
described above. Then, the total costs including removal
amount to €13,100. In Baden-Württemberg, due to the
fixed subsidy amounts, the subsidy per hectare does not
change and continues to be €7,215 (i.e. 55.1% with
removal). In Schleswig-Holstein, on the other hand,
due to the percentage type (85%) of subsidies, €11,135
is subsidised (i.e. the same amount in the case with or
without removal). Thus, if the (legally required) removal
of a plastic-based treeshelter is priced into the total sum
of costs, the state funding rate in Baden-Württemberg
decreases, while in Schleswig-Holstein it remains the
same according to the specifications, but of course the
absolute funding amount increases. Schleswig-Holstein
thus also supports removal of treeshelters, although it
would legally be the owner’s duty.
In the case of fencing as a protective measure, only
the procurement and installation costs are taken into
account in the first step. The removal of fencing can be
priced again at €3/rm, so that total costs of €23,100 can
be expected, including dismantling. Due to the fixed
subsidy amounts in Brandenburg, €10,050 (i.e. 43.5%
with removal) would still be subsidised. In Saxony-
Anhalt, on the other hand, €19,635 (i.e. 85% with
removal) would be subsidised due to the percentage
type of state subsidies. Thus, if the (legally required)
removal of fencing is included in the cost sum, the rate
of subsidies in Brandenburg decreases, while in Saxony-
Anhalt it remains the same according to the specifica-
tions, but the absolute funding amount increases. In
Saxony-Anhalt, the subsidy thus also encourages
removal activities.
Differences in levels of subsidies between the chosen
states are justified by forestry policy and such differences
can be considerable. So far, however, no evaluation of the
very different funding conditions in Germany, let alone in
Europe, have been carried out. It is obvious, however, that
the obligation to remove plastic-based treeshelters or fencing
made from metal has not yet been built into the state funding
guidelines. That is, the opportunity has not yet been taken to
support the clear legal requirement, but the lack removal
practice, by detailing state aid and subsidies with clear
guidelines.
Decisions between choosing treeshelters or fencing
are thus complex and require knowledge of operational
costs, government funding and many technical details
such as the length of the fence or the number of shelters
required for the individual protection of a particular tree
species, and all this per unit area (i.e. hectare). To
support decision-making in a multi-criteria environ-
ment, Helfenstein et al. (2017) supposed and setup an
app-based decision support system (DSS) called ‘tree-
shelter & fence calculator’. It is designed to determine
whether the use of treeshelters makes sense in the first
place or whether setting up fencing would be prefer-
rable. The software allows inserting costs based on pre-
installed schemata or manual inputs, so regional differ-
ences in costs can be adopted (Figure 5).
As a result, the app offers an output on the breakeven
point at 1249 ash plants. When planting more ashes than
the break-even point, a fencing measure is recommended.
Below the break-even point, a protective measure for indi-
vidual trees with treeshelters is preferable.
Future pathways for treeshelters
From a European perspective, the ecophysiology of young
seedlings in classic plastic-based treeshelters has been investi-
gated in depth for tree species that are relevant to European
silviculture. Thus, no further experiments are expected in the
near future. However, innovative types of treeshelters that are
not plastic-based and comply with legal prescriptions from the
forestry and circular economy laws are expected to be devel-
oped soon. Such new treeshelters will need to be evaluated
against classic ones from several perspectives: tree growth and
yield as well as tree physiology. As a recent trend, new devel-
opments have also emerged in Europe and Germany that
critically assess plastic products and especially microplastics
due to their unclear or even negative effects on the environ-
ment (e.g. Ng et al. 2021; Qi et al. 2018; Yang et al. 2020). Such
new dynamics in the natural sciences also have implications
for the use of plastic-based materials or objects in forest
management. Furthermore, the clear legal situation in
Germany, as presented above, shows a compulsion for the
Figure 5. Case study ‘comparison of fencing vs. treeshelter including removal’, with the following cost schemata: 900 ash plants (Acer pseudoplatanus) with a unit
cost of €0.32/plant, a planting cost of €0.74/plant and a tending cost of €0.15/pc. The length of the fence is 400 m and includes the cost of installation (€4.67/rm),
the cost of maintenance (€4.67/rm) and the cost of removal (€4.67/rm). The costs of treeshelters include the unit cost (€1.65/piece), the cost of installation (€1.61/
piece) and the cost of removal (€1.25/piece).
6Y. GRAF ET AL.

complete removal of old treeshelters with subsequent reuse or
recycling according to the principles of the circular economy.
We thus expect a major challenge to remove old protection
measures from their estates in response to modern societal
attitudes criticising the use of plastics in close-to-nature for-
estry. For us, removal of such old shelters after the service life
seems to be the major activity in a “plastic-reduction strategy”
for European forestry.
Recently, there have been remarkable advances of certifi-
cation schemes on forest management in Germany towards
requiring treeshelters that are not based on fossil fuel
resources and that are fully degradable under forestry con-
ditions. For example, FSC (Forest Stewardship Council)
addresses the issue of treeshelters in Forest Standard 3–0
under Standard 10.12.1 (FSC Deutschland – Verein für ver-
antwortungsvolle Waldwirtschaft e.V 2018). Here, forest
owners certified according to this standard are obliged to
remove old treeshelters. Similarly, PEFC (Programme for the
Endorsement of Forest Certification) certification with its
new standard revision (Germany) in 2020 added
a formulation now integrated into the PEFC standards. It
restricts use to certain types of treeshelters: ‘To protect the
forest ecosystem from plastic residues, the use of products
made from fossil-based materials, such as treeshelters, fen-
cing/ browsing/ debarking protection, and marking tapes, is
avoided as far as possible. Where available on the market and
economically reasonable, products whose materials are
derived from renewable resources should be used.
Treeshelters that are no longer functional and those that
have fulfilled their intended purpose are removed from the
forest and disposed of properly’ (PEFC Deutschland e.V
2020).
Although a detailed investigation of the legal and economic
situation of the use of treeshelters in Europe as a whole is still
pending, parallel developments and initial situations are
expected to happen soon at such a supra-national level. We
also expect that public procurement rules will better include
aspects of sustainability as well when buying treeshelters and
other by-products – for example, cable ties. Here – as forests in
Germany and Europe are partly publicly owned – public estates
could act as change agents to foster new and even more inno-
vative types of treeshelters.
Derived from previous findings, reflections and today’s
public attitude on micro-plastics and plastic-based residues
in the environment and forests, we define what could be
meant by innovative treeshelters and thus outline future
pathways to the next generation of such protective measures
as part of a plastic-reduction-strategy in European forestry.
Four requirements are set, each of which should fully be met.
Innovative treeshelters replacing classical plastic-based
ones should be:
(1) manufactured from 100% agricultural and forestry
raw materials from sources with a certificate on sus-
tainable management (biobased);
(2) fully degradable under forest conditions, without release
of pollutants and microplastics, proven by laboratory
and real forest-on-site certifications (biodegradable);
(3) at least be equivalent on comparison of functional-
ities, such as length of service life, and economic
efficiency, such as full cost calculation (fully
functional);
(4) advantageous in the life cycle assessment (LCA)
compared with classic plastic-based treeshelters
(equal or better in LCA compared with plastic-
based products).
However, recent developments have led us to be somewhat
sceptical, especially when assessing new products recently
appearing on the market from a perspective defined by the
first two requirements. For requirement 1, products adver-
tised as ‘biobased’ need further information regarding what
is meant by “biobased”. Even though there are definitions
and standardised methods to determine the amount of bio-
based material (e.g. ISO 16620-1:2015-04 2015; DIN EN
16785–1:2016-03 2016; ASTM D 2021:2021 2021), producers
mostly avoid marking the amount of biobased material on
the product unless they reach 100%. This may mislead cus-
tomers when buying biobased products. For requirement 2,
advertising products as biodegradable always needs to be
accompanied with additional information about the
intended length of service life and its environmental condi-
tions. The following examples outlines some of the differ-
ences in standards and definitions for complete
biodegradability:
(1) Industrial composting: 90% degradation must be
reached in 6 months at temperatures of 58 ± 2°C
(DIN EN ISO 13432:2000–122,000);
(2) Garden composting: 90% degradation must be
reached in 12 months at temperatures of < 30°C (AS
2010:2010 2010);
(3) Soil: 90% degradation is reached in 24 months at tem-
perature of 20–28 ± 2°C (DIN EN 17033:2018-03 2018).
The crucial point is that testing biodegradability is done in
environmental conditions that differ greatly from condi-
tions on the forest floor or in their top soil. Thus, tree-
shelters tested for biodegradability according to any of the
standards mentioned above do not necessarily fully
degrade in a forest environment within Europe (Graf and
Hein 2020). Thus, an upcoming major challenge when
developing fully biodegradable treeshelters will be to find
a testing environment that is in line with biodegradation
under boreal, temperate or semi-arid forest site
conditions.
Finally, in the plastic strategy of the European Union
(European Commission 2018), biobased and biodegrad-
able plastics are viewed as both a risk and an opportunity.
While it is feared that biodegradable materials could
enhance reckless littering, it is also recognised that there
are products with a high risk of remaining in the environ-
ment. Therefore, biodegradability can be a worthwhile
feature. To ensure the correct use of biobased and biode-
gradable materials, the European Union demanded
recently an explicit level of information provided to
consumers.
When including aspects on biobased or biodegradable
products as well as LCA into reflections on treeshelters,
fences, costs and environmental impacts, it is obvious
that making decisions is becoming even more complex.
We thus expect that DSS on the topic will need further
development of sophisticated apps and software tools as
described above. In addition, to make it more beneficial
JOURNAL OF FOREST RESEARCH 7

for users around the globe, more types of treeshelters
(e.g. also from Asia), as well as currencies other than
the euro and the U.S. dollar should be added.
Conclusions
Although treeshelters were invented more than 40 years
ago, there are ongoing technical developments in Europe
towards upcoming topics like biobased and biodegrad-
able products. In addition, there are considerable pro-
blems with insufficient removal of old treeshelters after
their service life in European and especially German
forestry. These problems partly prevent a portion of
the public from accepting modern silvicultural strate-
gies. Filling such gaps about the removal, improvements
towards biobased and biodegradable materials, enhanced
regulations of subsidies and pursuing legal situations by
law or certifications schemes of treeshelters could con-
tribute to further improvements of sustainable forest
management in Germany and Europe.
Acknowledgments
This work was supported by the FNR-Waldklimafonds (German Federal
Agency on Renewable Resources-Forest Climate Fund/German Federal
Ministry of Food and Agriculture & German Ministry for the
Environment, Nature Conservation and Nuclear Safety) within the pro-
ject “TheForestCleanup” under the Grant [FKZ 2219NR425], www.the
forestcleanup.de as well as by the German Federal Ministry of Food and
Agriculture & Federal Office for Agriculture and Food within the
German-Japanese project “3Arrows” under the Grant [28I-038-01].
Disclosure statement
No potential conflict of interest was reported by the author(s).
Funding
This work was supported by the Bundesanstalt für Landwirtschaft und
Ernährung [28I-038-01]; Fachagentur Nachwachsende Rohstoffe [FKZ
2219NR425].
ORCID
Yannic Graf http://orcid.org/0000-0003-2544-1219
Sebastian Hein http://orcid.org/0000-0002-4009-9282
Anton Sebastian Schnabl http://orcid.org/0000-0002-2804-4211
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