Biodiversity and Habitat in the garden/farm/landscape, why it is important and how we are attempting to measure it.
Last season we started a new survey in an attempt to gain an understanding of the biodiversity within various habitats of a polyculture garden/farm/landscape. During this post I’ll introduce the garden we carried out the surveys in, overview the habitat types within the garden that we looked at, I’ll present the survey protocol, share the results with you from the late Summer Survey and end with some discussion of the survey and results.
But first I want to take this opportunity to let you know that we’ve just launched a brand new Regenerative Landscape Design — Online Interactive Course — How to Design, Build and Manage Polycultures for Landscapes, Gardens, and Farms.
You can find out more about the course here to see if it tickles your fancy :) and if you’d like to take part we are currently offering a 20% discount to the first 10 people to enroll. Register here with promo code 1st102020 to take advantage of this offer.
We are looking forward to providing you with this unique online learning experience — as far as we know the very first of its kind! If you are looking for reasons why you should do this course and whether this course is suitable for you, take a look here where we lay it all out.
Back to the post and let’s start with what’s the point of recording biodiversity in the first place.
Why do we need to record biodiversity in the first place?
Our project mission is to develop and promote practices that can produce food and other resources for humans while enhancing biodiversity. To encourage biodiversity in our gardens, we include a variety of habitat into the landscape design, including native wild habitats (at various stages of succession) and cultivated habitats. The gardens are, essentially, a mosaic of habitat. Seeing as we are looking to enhance biodiversity within our gardens we must have the means to record the diversity within the various habitats. Our aim is to use this information to guide our land management practices specifically in terms of what ratio of land we should dedicate to wild native succession habitats and to what degree we can work within these habitats without disturbing the suitability of the habitat for other organisms i.e without disrupting the biodiversity. Furthermore, we would like to see how our cultivated habitat types i.e annual and perennial polyculture, compare to the wild habitat.
Various habitats within our Polyculture Market garden Plot — Aponia (Aquatic habitat not included)
See here for this gardens location on our project map. For habitat, description see below
To do this completely we would need to include plants, fungi, animals (invertebrates, birds, mammals, reptiles, amphibians) and microbes. Quite a task by any standard and currently beyond the capacity of most people and projects, including ours. Actually, we do have good general records of plant — mammal — bird — reptile and amphibian species that inhabit our gardens (Dylan has started to add these to our website that you can find here if you are interested) For seasonal surveying and tracking changes over time I believe that a good way to assess the general biological diversity is to study Invertebrate diversity i.e spiders, insects, bees, etc. Invertebrates largely rely on plants for food and shelter and Invertebrates are often relied upon by birds and mammals further up the food chain as they make up a significant portion of the larger animal’s diet. It seems that within our environment at least when you have high levels of invertebrate diversity you will likely have high levels of plant and larger animal (vertebrate) diversity too.
Just a few of the organisms that inhabit our gardens
As a side note, I believe strongly that a global standard for accurately recording and accounting for biodiversity is probably the most important factor for transitioning into regenerative agriculture and without this standard, regenerative agriculture will most probably remain a trendy, marginal application meeting only a tiny percentage of global food demand. With a global biodiversity recording and accounting standard established it can be used across the planet to provide incentives for activities that are enhancing or at the very least sustaining biodiversity levels and withdraw incentives and issue penalties for those activities that result in lowering biodiversity. This is a huge discussion beyond the scope of this post and the development and application of such a standard is something that humans, with skills that I do not possess, could develop and would involve engineering new hardware and software technologies and the coordination of a massive global academic and political collaborative effort. Certainly not beyond our collective reach but probably one of the tougher challenges of our time.
For now, I will focus on what I can immediately do and so have aimed to develop a super simple low tech method to survey invertebrate diversity within our garden habitats. The goal of the survey is that it should be simple enough that anyone can use it and that the data collected should be good enough to draw some useful conclusions.
First, an overview of the garden where we are carrying out the Surveys.
Garden Overview
Location: Shipka, Bulgaria, Southeast Europe
Climate: Temperate
Köppen Climate Classification — Dfc borderline Cfb
USDA Hardiness Zone: 5b (conservative) — 7a (risky)
Latitude: 42°
Elevation: 565 m
Average Annual Rainfall: 588.5 mm
Prevailing Wind: NW & NE
Garden Name: Aponia — Polyculture Market Garden
Garden Location on our Project Map — See here
See here for this gardens location on our project map
Within this garden, we have identified a number of pre-existing habitats and have created some habitats. What follows is a description of those habitat types within the garden.
Habitat Types
Habitat types refer to distinctly different regions within an area and in this case, are determined by the composition and age of the plant species within those areas. We have identified 6 habitat types within this garden that fall under the following categories — Wild Habitat, Semi Wild Habitat, Semi Cultivated Habitat, and Cultivated Habitat.
Wild Habitat Type
Late Scrub
Early Scrub
Semi Wild Habitat Type
Mixed Species Meadow
Semi Cultivated Habitat Type
Mixed Species Hedgerow
Cultivated Habitat Type
Perennial Polyculture
Annual Polyculture
It should be noted that the cultivated habitat types as presented above were abandoned horticultural land and were heavily grazed by tethered horses before we started the development of the garden. This land, if left unattended, would succeed to a habitat very similar to the other habitats on the site namely — Mixed Species Meadow to Early Scrub to Late Scrub and would eventually form Woodland. When working with habitat types within your landscape it’s important to have a good understanding of the successional pathway of the vegetation in order to properly appreciate the dynamics of the land and the species that inhabit each successional stage. This information will help you manage the land, specifically the potential for biodiversity, properly.
An excellent classification system for habitat type has been developed The UK Habitat Classification and can be downloaded from the bottom of their homepage here. Our classification system follows this broadly but I have made some adaptions to make it more relevant to our polyculture design, implementation, and management strategy.
The map below shows these various habitat types within our 8-year-old Market Garden, Aponia.
Habitat Type Detail
The following information only partially includes the diversity of plant species within each habitat for the month that we carried out the survey i.e August. We intend to make a full record of all the species in each habitat across the season (to account for the seasonal succession of annual and ephemeral species) next year during our Polyculture Study 2020 and provide labeled illustrations of the placement of plants within the cultivated habitats.
Late Scrub — Wild Habitat Type
Wild Habitat Type
Late Scrub
Scrub is often found where woodland starts or ends; or in abandoned fields. Scrub or scrubland is generally vegetation dominated by early succession shrubs and small trees such as brambles, sloes and hawthorn. Some of the species may reach a height of 3–4.5 m and when mature scrub can resemble woodland. Many scrub plants are pioneer species, which grow fast and can colonise open habitats quite rapidly. These plants often spread by suckers (vegetative formation of a new stem and root system from an adventitious bud of a stem or root) and many of these plants have thorns or spines to protect them from herbivory.I’ve divided the scrub habitat we have on our plots into Early and Late Scrub. Late Scrub is dominated by small trees and shrubs and is generally 6–12 year old wild growth over grassland. Early scrub succeeds to late scrub on this siteLate Scrub — Summer Species ListLatin NameOccurrenceFormPrunus insititiaDominantTreeJuglans regiaFewTreeHelix hederaPatchesGroundUrtica dioicaFewHerbRobinia pseudoacaciaEncroaching into the area from the highway plantingTreeBryophytes — MossMany PatchesGroundVariety of herbs and grasses on the margins of the habitat to be identified
Early Scrub — Wild Habitat Type
Wild Habitat Type
Early Scrub
Scrub is often found where woodland starts or ends; or in abandoned fields. Scrub or scrubland is generally vegetation dominated by early succession shrubs and small trees such as brambles, sloes and hawthorn. Some of the species may reach a height of 3–4.5 m and when mature scrub can resemble woodland. Many scrub plants are pioneer species, which grow fast and can colonise open habitats quite rapidly. These plants often spread by suckers (vegetative formation of a new stem and root system from an adventitious bud of a stem or root) and many of these plants have thorns or spines to protect them from herbivory.I’ve divided the scrub habitat we have on our plots into Early and Late Scrub. Early Scrub is dominated by shrubs and is generally 3- 6 year old wild growth over grassland. Early scrub succeeds to late scrub on this siteEarly Scrub — Summer Species ListLatin NameOccurrenceFormRubus spp.DominantShrubPrunus insititiaFewSaplingJuglans regiaFewSaplingClematis vitalbaScatteredClimberBryophytes — MossFew PatchesGroundVariety of herbs and grasses on the margins of the habitat to be identified
Mixed Species Meadow — Semi Wild Habitat Type
Mixed Species Hedgerow — Semi Cultivated Habitat Type
Annual Polyculture — Cultivated Habitat Type
Perennial Polyculture — Cultivated Habitat Type
Micro habitat
Our garden designs also include a variety of microhabitats such as rock piles, small and large ponds, gravel pathways, stick piles, rotten log piles, helping mats, tree stumps. These are often placed within a variety of habitat types and are not considered in the survey. A survey of our microhabitats will make a good continuation of this study for the future.
Micro habitat from the gardens
You can find a full education on integrating and managing habitat in your garden/farm/landscape in our online Polyculture Design Course. We have multiple sessions of the course dedicated to habitat and cover extensively and coherently how to identify habitat types on your land. We will also cover ecological succession, how to identify the typical flora and fauna species of your habitat, how to make habitat maps, how to develop, maintain and manage habitat, and look at the productive potential of each habitat. We encourage you to bring your own garden/land/farm plots into the course for discussion. You can register for the Polyculture Design Tutorial Here. We are planning to launch the course in July 2020
So now let’s look at the Survey Design and how we aim to gain a measure of biodiversity within each habitat type.
Our Survey
Each of the 6 habitat types are surveyed for the number of unique species observed in 2 pitfall traps within each habitat type and 10 canopy observations at different locations within each habitat type. These surveys are carried out at the same time every first and second Monday and Tuesday of the months April to September over a period of 3 years.
The time and date — weather conditions (cloud cover — temperature — wind ) and rainfall received since the last survey are all recorded before we start. (rainfall received since the last survey is only recorded for weeks 2 and 3 of each month)
The Pitfall Traps
Two pitfall traps are set within each habitat type. Each trap is labeled for recording purposes. The traps are set on Monday morning, left overnight and emptied onto white trays on Tuesday morning.
The pitfall traps labeled ready to take a position in the habitats.
The number of unique species is counted within each trap and an average of the two traps per habitat is taken to provide the average number of unique species found within each habitat type. After emptying the traps, lids are placed on the jars and the survey is repeated the week after. The below image shows the locations of the traps within each habitat type.
Simon setting a pitfall trap
Shahara Khaleque made a couple of videos that show the habitat types and how we undertake the pitfall traps surveys. You can find part 1 here and part 2 here. Thank you Shahara :)
Canopy Observations
A 50 m trail within each habitat is determined as shown by the red dotted lines in the below image and 10 locations labeled 1–10 are fixed 5 m apart along the trail.
At each location the observer stands and observes within their 2 -3 m field of vision (without turning head) for 2 minutes -1 min standing — 1 min kneeling and records the number of unique species they can see on the plant vegetation and on the ground.
Protocol Invertebrate Survey — Canopy Observations
Find your starting mark
Set timer to 2 minutes
Face the habitat and count the number of different species* within your 2–3 m field of vision without turning head. 1-minute standing and 1-minute kneeling
After 2 minutes walk to the next mark
Repeat 2 to 4 until you have completed 10 surveys.
Species you have seen in previous locations are counted again (start new species-count after every change of location)
*Different species = Do not count individuals, count visibly different species, e.g. :
3 black ants and 1 red ant = 2 species
1 big black spider and 1 small black spider, hard to say if it is young/old or male/female = 2 species
1 small spider and 1 big spider that are clearly the same species = 1 species
Flying species: Bypassing flying insects do not count. Insects hovering (to feed on nectar/pollen) or landing in your field of vision do count.
Here is Shahara taking canopy observations in the Early Scrub Habitat
To account for discrepancies between individuals’ vision and interpretation of what should be counted as individual species we undertake the canopy survey twice with a different person counting a different habitat and rotate who does which habitat each week.
The data for both surveys are recorded on printed sheets as seen below. If you would like copies of the sheets, contact us via the form at the end of the post.
How we process the data
The data gathered for all of the surveys in each habitat is averaged. For example, in the Late scrub if five unique species were counted in pitfall trap 1 and three unique species counted in trap 2 the total record for pitfall traps in this habitat would be 4. Likewise, if eight species were counted during canopy obs 1 and four species were counted during canopy obs 2 the total record for the canopy observations for this habitat would 6 species.
We then take an average of both the pitfall trap and the canopy surveys within each habitat for the overall species diversity of each habitat type.
Finally, the results from each month are averaged to give us a monthly average of the number of unique species in each habitat and the monthly results are averaged to give a season average for each habitat.
Hope that all makes sense
The Results
Invertebrate Survey
The below table shows the number of species we recorded from each habitat type in weeks 1 2 & 3 of our August Survey.
Weeks 1–3 — Results Summary — Based on the average number of unique species counted in Pitfall and Observations
Week 1–1 day after significant rainfall
Week 2–8 days after rainfall
Week 3–15 days after rainfall
Rank
Habitat
Number of Species
Rank
Habitat
Number of Species
Rank
Habitat
Number of Species
1
Annual Polyculture
7.575
1
Annual Polyculture
3.775
1
Annual Polyculture
3.825
2
Perennial Polyculture
6.5
2
Mixed Species
Meadow
3.425
2
Mixed Species
Meadow
3.475
3
Mixed Species
Meadow
5.8
3
Early Scrub
2.9
3
Early Scrub
3
4
Mixed Species
Hedgerow
4.575
4
Perennial Polyculture
2.525
4
Perennial Polyculture
2.3
5
Early Scrub
4.2
5
Mixed Species
Hedgerow
2.2
5
Mixed Species
Hedgerow
1.875
6
Late Scrub
1.85
6
Late Scrub
1.7
6
Late Scrub
1.575
The August survey revealed that the Annual Polyculture was the habitat that showed the highest levels of unique invertebrate diversity and that Late Scrub showed the lowest levels of diversity.
Total — Average for each habitat (rounded up)
Rank
Habitat
Number of Species
1
Annual Polyculture
5.0
2
Mixed Species
Meadow
4.2
3
Perennial Polyculture
3.8
4
Early Scrub
3.4
5
Mixed Species
Hedgerow
2.9
6
Late Scrub
1.7
It’s obviously too early to draw any conclusions based on 1 month of surveying but it looks like a promising start for our cultivated habitats. I think a significant part of the reason why invertebrate diversity was higher in the cultivated areas is that they are irrigated at least bi-monthly and water is probably the single most important factor concerning biodiversity especially the ground invertebrates. I expect that the early spring surveys will tell a different story with the abundant rainfall bringing life to the Scrub areas. The mixed-species meadow results were as expected and even without irrigation were teaming with flying insects taking advantage of the pollen and nectar resources on offer. I’ve really enjoyed thinking about this survey and carrying it out and hope that we have managed to at least catch a glimpse of the diversity within our garden habitats and look forward to gathering a full season of data next year and for the next 3 years.
Shortcomings of the Surveys
Our aim is to keep the survey as simple and replicable as possible without sacrificing the validity of the data. It seems to me that the barriers to entry for the majority of people when carrying out such a survey will be costs — expertise and time. I believe we have certainly addressed the cost and expertise barriers with the design of this survey and have reduced the amount of time needed to carry out the survey to something that is quite manageable providing you have a small team of 4- 6 people that are willing to give 30 minutes of their time 12 times a year and you are prepared to co-ordinate them and process the data. (the sheets we use are programmed to do the math so all you need to do is enter the data). It’s also possible for one person to complete the survey alone but it’s almost certainly going to be tedious.
Here are the main shortcomings we have identified so far. If you can see more please do let us know and better still provide a solution that fits within the goals of the survey design.
Because we are not using ethanol in the pitfall traps (commonly used to kill what falls in the traps), it’s possible that predators may fall in and eat prey species before we can count them.
The canopy observations do not account for nocturnal invertebrates
The canopy observations from the habitat types with tall shrubs and trees do not account for invertebrates in the higher canopy. We could use a “beating tray” observation for this but for some of the habitat such as early scrub and hedgerow, it will be difficult to set this up.
We are not accounting for the influence the surrounding habitat has within our habitat types i.e in some cases uniformity of habitat type, although, may not support a wide range of invertebrate diversity could be essential for certain mammals or bird that may only inhabit the area at certain intervals of the year.
Biodiversity metric alone cannot be used to signify environmental health — soil health — water quality — air quality, productive capacity in terms of meeting human needs and the stability/resiliency of the state should also be considered.
As we are not identifying the species and have limited knowledge of entomology we may be counting unique species when in fact they are male or female, larvae/adult or at different instar stages. Reliable identification apps for invertebrates will produce, much more valid data as we will be able to record the individual species. I expect this technology will be available in the not too distant future, at least for identification to the group level which can be very helpful for our purposes.
For future surveys we will develop a simple category ID list for i.e ants — bees — winged insect unknown — beetle and identify the most common species in order to have a better understanding of the organisms within each habitat and hopefully to identify how these organism relate to productive capacity i.e pests, borgs (beneficial organisms), neutrals.
If you have any suggestions on how we can improve the survey please do let us know and if you would like to try the survey yourself, fill in the form below and I’ll send you the record-keeping spreadsheets and protocols and our data if you wish.
Thank you, Simon and Eva, for writing the protocol for the canopy observation survey and for your help and feedback on the design of the Survey and thank you to the polyculture study crew 2020 for carrying out the first season of the surveys.
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Thank you to all the people that have already donated to our project and to our customers, friends, family, and volunteers that make it all possible and thank you to Chris Kirby Lambert and Peter Alfrey for carrying out invertebrates surveys in the past and helping us develop our understanding of invertebrate diversity within the gardens. You can find Chris’s protocol and results here and Peter’s observations here.
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