Relation between Critical load Exceedance and Species Loss. Arjen van Hinsberg

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1 Relation between Critical load Exceedance and Species Loss Arjen van Hinsberg

2 Outline Introduction Why should we try to derive dose-response functions between CLE and species loss? Results Calculation of Dose-response Functions Conclusions & Discussion

3 Nitrogen deposition & biodiversity Global goal: a significant reduction of the current rate of biodiversity loss in 2010 EU goal: halt the loss of biodiversity in 2010 EEA: CLE is one of the proposed indicators to monitor progress in Europe

4 Evidence from experiments Effects of Nitrogen-addition Empirical Critical Loads Control +N

5 Evidence from complex dynamic models Effects are likely given the relation between: Deposition Soil conditions Vegetation structure Plant species occurrence Occurrence of butterflies, birds, Changes take time: delay in effects and recovery

6 Evidence from monitoring/observations (1) Large changes in oligotrophic species Mean change index (+/- s.e) Change from to Low Ellenberg-N Intermediate High Ellenberg-N 'UK' Ellenberg N value

7 Evidence from monitoring (2) Abundance of sensitive species is decreasing over time

8 Strong evidence, however.. Technical indicator AEE, Exceedance of 5 th percentile of CLnutN Health effects of air pollution Mortality Years of life lost Excess death rate

9 How can we relate CLE to species loss? 1. Dose-effect relations derived from experiments (R. Bobbink) 2. Simplifications of available complex dynamic models % Molinea 0,20 0,15 0,10 0,05 0,00 Transition heather to grasslands (SMART/MOVE) after 1 year after 10 years after 50 years after 100 years N-deposition 3. Regression analyses on field observations

10 Correlation between CLE and occurrence of threatened/protected/rare species Birds Log-linear regression: Relative number of species = 1 (1 + exp(-a - b * CLE)) % characteristic species Butterflies

11 Methods (3) Ecosystem specific analyses: Dry heath; Wet heath; Bogs; Forests on dry sandy soils; Forests on rich sandy soils; Wet/moist oligotrophic grasslands Focus on characteristic species Focus on threatened/protected species: Birds; Butterflies; Plants; All Empirical CL & Modelled CL s Tested: Significance; Linearity; Interaction with other factors (management, area,..)

12 Results (1): Negative effects of Nitrogen deposition Dry heath Forests on dry sandy soils Moist/wet oligotrophic grasslands % characteristic species Conclusions: many significant negative relations CLE % characteristic species often simple linear relationships much unexplained variation (many other factors determine species occurrance) % characteristic species CLE CLE

13 Results (2): negative effects also found in fauna species Forest (poor) Forest (rich) Oligotrophic grassland Dry heath Wet heath Bogs Birds -0,31-0,19-0,31-0,17-0,43-0,73 Plants -0,39-0,66 0,01-0,41 0,12-0,03 Butterflies -0,03 0,19-0,91-0,39 0,06 0,72 Total -0,39-0,22-0,27-0,28-0,07-0,22 = significant at p<0,05 Value = linear regression coefficient

14 Results (3): simple dose-response functions

15 Results: large stock at risk At 500 mol/ha/yr exceedance Birds Forest (poor) -8% Forest (rich) -5% Oligotrophic grassland -8% Dry heath -5% Wet heath -11% Bogs -9% Plants Butterflies Total -17% -9% -24% -8% -35% -10% -14% -16% -10% At 1000 mol/ha/yr exceedance -17% -30% -10% -43% -15% -58% -10% -27% -29% -22% -20% -18% -15% -19% -19%

16 Conclusions/Discussion Monitoring shows ongoing loss of N-sensitive species Observations show large negative effects of CLE on biodiversity Effects are not only found in plants and forests Problem (1): are we in steady state? Problem (2): limited information at low deposition levels! Current complex dynamic models might help: by describing the modifying factors influencing the dose-response functions. and/or by providing simplified dose-effect functions Extend the study towards low-deposition areas

17 Way to go? Use the empirical and modelled doseresponse functions to derive biodiversity-relevant and understandable indicators. Simplifications of current complex models might increase their use. Empirical and modelled Dose-effect functions between CLE and biodiversity