Ecosystem Impacts and Economic Costs of Climate Change

1. Ecosystem Impacts and the Economic Costs of Climate Change Dr. Rachel Warren Tyndall Centre, University of East Anglia Funded by

2. Outline • Quantifying the economic impacts of climate change that are avoided by mitigation • Why we used the PAGE09 model • Issues with the cost benefit approach to economics of climate change • Role of ecosystems and their services • Quantifying the impacts of climate change upon biodiversity that are avoided by mitigation • Other ecosystem impacts

3. Mitigation can avoid up to one half of aggregate economic damages by 2080s ***Both physical modelling and economic analysis produce same key finding***

4. PAGE09 Economic Model • Excel 2010 workbook with @RISK 5.7 add-in • 8 regions • 10 analysis years • 4 impact sectors including discontinuity • Look at 2 policies and their difference • 112 uncertain inputs • 100000 runs to calculate distributions of outputs • Choice to include/exclude equity weighting

5. Mitigation benefits in economic and physical metrics • Early, stringent mitigation can avoid a large proportion of the aggregate economic impacts of climate change that would otherwise occur during the second half of the 21st century • If global emissions peak in 2016, around one half of the global aggregate economic impacts can be avoided, • if mitigation is delayed so that emissions peak in 2030, only around one third can be avoided

6. Comparison with cost-benefit analysis • Sometimes recommends ‘optimal’ pathways to eg 3°C or higher • Derives optimal tradeoffs between mitigation, damage and sometimes, adaptation • Incomplete representation of the climate system, climate change impacts, and adaptation. • Depends on uncertain discount rate, equity weights, climate sensitivity, cost of adaptation ...new knowledge renders it sub optimal • No single decision maker or budget holder • Subjective valuation of impacts

7. Outcomes of cost-benefit analysis is determined by input assumptions

8. IPCC AR5 ‘Reasons for Concern’

9. ‘Burning embers’ and ‘Representative Concentration Pathways’

10. 60% of plants and 33% of animals lose ≥50% of their climatic range by 2080s. 50,000 widespread species

11. Losses reduced by 60% in 2°C pathway, 40% in 2.5°C pathway 50,000 widespread species

12. Mitigation reduces the land area where climate becomes unsuited to 75% of species now present BIRDS AMPHIBIANS PLANTS MAMMALS

13. Areas remaining climatically suitable for 75% of plants currently present: 2°C plant refugia

14. Areas remaining climatically suitable for 75% of plants current present: 3.5°C plant refugia

15. Plant areas of concern at 2°C Wallace Initiative

16. Plant areas of concern at 3.5°C Wallace Initiative

17. How mitigation ‘buys time’ for adaptation

18. Mitigation avoids significant terrestrial carbon loss in 2080s

19. Caveats: other impacts on ecosystems • Climate change also affects productivity • Climate variability will impact biodiversity • Changes in phenology or distribution may result in temporal or spatial ‘mismatch’ • Dispersal ability constrained by man made barriers • Species extinction (not covered here) • Loss of Arctic summer sea ice

20. Conclusions 1 • Avoided impacts for aggregate economic impacts, biodiversity and ecosystem services are large and increasing throughout the 21st century • With 2°C target, ~50% of global aggregate economic impacts can be avoided • In 2.5°C target~33% can be avoided • 60% of plants and 33% of animals likely to lose ≥50% of their current climatic range by the 2080s. • With mitigation, losses reduced by 60% in 2C target, 40% in 2.5C target • Avoiding biodiversity loss also avoids loss of substantial amounts of terrestrial carbon • Avoided impacts increase with time • Stringent mitigation buys decades for adaptation • Delay in mitigation reduces avoided impacts