Biodiversity metrics – a way forward

Ed Rowe

Let’s GROW

GoalRealityOptionsWay forward

Principles

“Biodiversity” means different things to different peopleWe need an operational definition...on a single axis Wilfried Winiwarter: “only one dimension (endpoint) possible”

0 5 10 15 20 25 30 35 40 4505

101520253035

N deposition kg ha-1 yr-1

Spec

ies

Rich

ness

0 5 10 15 20 25 30 35 40 450

0.20.40.60.8

11.21.41.6

N deposition kg ha-1 yr-1

Stru

ctur

al in

tegr

ity

Goal: one metric (per habitat)

Index reflectingno net loss of biodiversity

N deposition

EUNIS classLv 3? (G1.6)

Reality

• Biodiversity is not easy to define• We have been discussing this topic for many years• The Call for Data 2012-14 gave us the opportunity to escape

Reality

slope

Ndep (eq ha-1 yr-1)average of range studied

R2 = 0.0001

Predicted by regression

Slope of Biodiversity Metric

vs. N deposition plot

Jaap Slootweg Summary of NFC responses to CCE Call for Data 2012-14

Are we using the right metrics?

Dani Kurz, Beat Achermann (Preliminary results, will be updated!)

Must N deposition damage biodiversity?

For the N pollution impacts research community – yes, obviously

we could just use deposition rate as an impact metric

...but, biodiversity specialists and the public don’t think of biodiversity in terms of nitrogen – sorry.

Although, nutrient-poor, less-productive habitats are usually thought of as having greater nature conservation value

“Why don’t we just...”

...use species-richness?

valued habitats are sometimes relatively species-poor

...use an index of even-ness, e.g. Shannon or Simpson?

valued habitats are sometimes dominated by one species

...use scarce / protected species

scarce species are often not present

Limitations of current models

Niches for scarce species are usually less well-defined we can’t predict values for metrics based on scarce species.

We can predict species-richness, at least statistically ... although mechanisms are not yet well-understood

We can predict habitat-suitability (MOVE, PROPS, MultiMOVE) ... but we can’t yet predict probability of occurrence – this would need

dynamic modelling of extinction / seedbank persistence / dispersal we should be a bit careful with language

Predicting abundance (e.g. cover) is really hard we can’t reliably predict values for metrics based on:• functional-group abundance (cover of Sphagnum, ericoids etc.)• relative abundance of species (e.g. Simpson, Shannon)

Although, these could be foci for model development

Options

• Need to be discussed

Way forward

• Accept that there is no “objective”, “scientific”, “value-free” definition of biodiversity• Find the people who should define biodiversity for your country• Maybe call it “habitat quality” rather than “biodiversity”• Allow them to discuss the topic freely• Remind them that we need a one-dimensional metric • Remind them that we need an answer within this century• Maybe ask them to rank a set of real examples of the habitat

Agreeing on a metric – things that might help

12 examples of “dry grasslands”

Species-richness

Ranking according to metric

Ranking according to specialists

CSM positives CSM negatives CSM +ves minus -ves

Forb / Total cover

Similarity to reference (mean) Similarity to reference (max)

Mean Ellenberg N

Rowe et al. 2014DivMet/AQ0828 report

E1 Dry grasslands

Way forward

If you really can’t get your biodiversity experts to engage...maybe you will have to decide.

UK and NL seem to be settling on “positive indicator-species”, a small set of typical/distinctive species for each EUNIS class

Conveniently, values for metrics based on these usually decrease with more deposition

Other metrics are available

ecro@ceh.ac.uk

Thankyou