Life is great!

A Patch Portrait
Collage of patch Wildlife with the perimeter and contour lines picked out with the names of patch species.

In some cases,especially the very large ones, these numbers are in the realm of 'guestimate' and indeed speculation

This a lot of life - where did it come from?

Life, the universe and everything

I sometimes find it instructive to look at an area and think what it would like without the living things. In short it would look similar to the dead, rocky surface of the moon.

Life has bestowed upon this, would be, barren surface a green cloak of living organisms. The breathing, growing, reproducing, eating, feeding, singing, scurrying, flying, flowering, beautiful exuberance – that is nature...

…and it all originates in space. Green plants trap the sun’s energy by photosynthesis allowing living things to rearrange atoms on the earth into living structures. These atoms ultimately originated in “The Belly of a Star” - almost every element on Earth was formed at the heart of a star.

I put a video explaining this process in a previous post Wren Song an Echo of the big bang

How were these numbers arrived at?

Kestrel (Falcon tinnunculus)

Common whitehroat
(Sylvia communis) patch map 
of singing males in 2016

Birds
I know the numbers of birds on the patch more accurately than any other group as I’ve counted them! So I can say with a reasonable degree of certainty that there are 2 Kestrels and with slightly less certainty that there are approximately 70 Common whitethroats.

Even though these are the figures with the highest degree of confidence, they are still going to subject to wide fluctuations and indeed errors.

The figure of 1,200 breeding birds is going to represent a minimum. There may well be three, four, five times this number at the end of the breeding season.

It’s interesting to note that around a quarter of these breeding birds are warblers (2016 Warbler survey), which being summer migrants will of course vacate the patch in autumn.

On the other hand, it’s likely that several hundred additional wintering birds – Redwings, Blackbirds, Robins, etc are present on the patch at various times in autumn.

Mammals

Small mammal jaw bones
from 3 Barn owl pellets
on the patch

It has been suggested that wild mammals densities in the UK can be calculated by assuming there are 2.25 mammals for each breeding bird¹. This would yield a figure of 2,700.

The number on the patch can’t possibly be that low however. The patch supports around 10 mammal eating birds (Barn & Tawny Owls, Kestrels, Buzzards). A single Barn owl alone requires at least 2,000 field voles in a year.

On the basis of typical field vole densities and the amount of vole-friendly habitat on the patch 20,000 seems a reasonable estimate. There will also be other abundant rodents and shrews so 40,000 is my rough ‘guestimate’.

Home Sapiens
This primate is a special case amongst the mammals. It constructs very obvious dwellings or ‘houses’ to use the technical term.  Given a UK density of 2.3 per dwelling, the patch population will be approximately 43.

This species can be hard to observe, as they frequently retreat inside the ‘houses’. However the best chance of seeing them is the morning, in fine weather, when accompanied by their companion animals, they exhibit a conspicuous behaviour pattern – ‘dog walking’ being the technical term.

Trees

100m² of the patch from
Bing.com

The aerial photographs provided by Bing.com are sufficiently detailed to allow trees to be counted. Google Earth is much less useful for this as it doesn’t directly use aerial photographs, instead it creates 3D ‘models’ of trees from aerial photographs (there is unlikely to be an exact 1:1 relationship between actual trees and modeled trees).

My figure of 20,000 is of course very much a rough approximation - based on counting the trees in several small areas of known size and extrapolating given the proportion of tree cover on the patch (again estimated from aerial photographs).

A very important caviat is that these are just mature trees – (i.e. the trees that form the canopy and are therefore visible for the air).

Lichens

...There are a lot of lichens!

Some old Oak trees on the patch have a large proportion of their bark covered by lichens, on the other hand some coniferous trees have very few. I attempted to get a sense of average numbers of lichen per trees and reckoned 1,000 was possible (although it could be much more).

So extrapolating from the number of trees we get a figure of 20,000,000. This figure is a 'guestimate' extrapolated from an estimate – so the margin for error here could possibly be large (Yet another caveat - trees are far from being the only lichen habitat on the patch - furthermore what constitutes an 'individual'?).

Money spiders (Linyphiidae)

...There are a lot of money spiders!

On some autumn mornings, grassy parts of the patch seem be almost completely covered in spider silk. The morning dew briefly makes visible this normally hidden phenomenon. In turn this allows an estimate of the number of webs per square meter (possibly 100 webs) and a figure extrapolated from the proportion of the patch which I estimated to be ‘money spider friendly’ (i.e grassland).

Here there is the, rather bold, assumption that the number of webs is equal to the number of spiders.  This is probably, approximately true at certain times of the year, however after the hatch of spiderlings takes place, there will be very many times more spiders on the patch.

The dewy spider web is an interesting example of, the way in which there is a huge amount of nature ‘out there’ – but most things we hardly ever see. Just by chance we occasionally find things that allow glimpses into a normally hidden world – what we get to see is the tip of nature’s ice berg.

Returning for a moment to the discussion of mammal numbers - owl pellets are another example of this. They give an indication of huge number of voles scurrying around in the undergrowth – maybe 20,000 on the patch.

Compare this with Wrens - the patch commonest bird with about 50 breeding pairs - I very frequently see Wrens whereas I hardly ever see, the much more abundant, voles. Wrens inhabit a similar "sense world" to ours - voles are almost invisible to us. Our brains may fool us into thinking we're getting the whole picture, but it is in fact a small fragment of the real world - the parts our limited senses allows us to perceive.

Grass moth  (Crambidae)

...there are a lot of grass moths!
Garden Grass Veneer
(Chrysoteuchia culmella)

There are several species of  'Grass Moth', Garden Grass Veneer, Agriphilla straminella and Agriphila tristella being the commonest. By day they camouflage themselves by sitting along grass stems, but can be very readily seen when they are disturbed and take flight.

On certain days late summer almost every step through the grassy parts of the patch seems to flush several of these moths. Again, this allows a ballpark estimation of patch numbers based on an estimate per square meter (10 would seem to be very conservative) and the proportion of the patch which is ‘grass moth friendly’.

Plants (i.e. Vascular plants)

10cm²   makeshift quadrats

To get an idea of plants numbers I looked at a number of makeshift 10 cm² quadrats .in different parts of the patch, then extrapolated to get a figure for the whole patch.

I wouldn’t want to make any great claims (or even any modest claims) for the accuracy of this method, as my sample size was small and not well randomised.

Still it allowed me to get a feel for the kind of numbers that might be involved.



Earth Worms, Insects (plus other arthropods), Springtails Protozoa, Bacteria
For these groups I used published data of densities (10¹³ bacteria, 10⁹ protozoa, 50³springtails, 5³ insects (plus other arthropods) per square meter of soil^2,3.

At the risk of labouring the point, the figures arrived are at here will have huge margins for error and in fact the difference between these figures and the actual figure could well amount to several orders of magnitude. Another obvious point is that these are just numbers in soil - there is a lot of the patch which isn't soil!

In the case of things like bacteria and protozoa is possibly safer to say numbers are astronomical.

How many species are there?

I have a good idea of the number of bird species are on the patch - 52 breeding species and 112 species seen, as well as dragonflies (13) and butterflies (20). As these are easily observable it’s highly unlikely that there are significant numbers additional species.

My patch moth list stands at 239 species – this figure could probably be doubled with more prolonged trapping. I’ve identified well over 200 species of both vascular plants and fungi. However for some very diverse groups such as Beetles, flies and spiders I’ve only scratched the surface.

I have identified getting on for 700 species on the patch and this could comfortably reach 1,000 with a few more years of ‘patch-watching’.

However this is likely to be a very different thing to the actual number of species. This is a still further iceberg tip  - the number of known species in the world is thought to be a fraction (maybe 1/5th) of the actual species.

This will apply to the patch – perhaps less so than a similar area of Amazonian rain forest, where there will be many more,  much less studied (the UK has perhaps the world most studied flora and fauna) species. Nonetheless it’s safe to say the number of species on the patch will never be known and it will far exceed the number that I find.

So nature is diverse! It has found many, many different ways of going about 'this thing called life' (to quote Jazzy B) – each of those ways represents a species.

So what can be gleaned from all this
1) There is a lot of life on the patch – as there is in most places on earth
2) This ‘living stuff’ depends on the sun and originated in space
3) Living things depend on green plants
4) There are a lot of species
5) There aren't many humans but they have a massive impact
6) In relative terms multi-celled organisms are rare – easily out numbered by single-celled organisms
7) What we see is the tip of the iceberg
8) There are occasionally ways of getting a glimpse of more of 'nature's icebeg'

…and my final conclusion – life is great!

Life is great

...definitely great

....totally great

^References
1 Matheny and Chan (2005)

² Brady (1974)
³ James Nardi (2007)

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