1. GLOBAL CHANGE THREATS TO HYDROLOGY & TERRESTRIAL ECOSYSTEMS: IMPACTS OF GLOBAL WARMING & SPECIES INVASION IN HAWAI‘I Thomas Giambelluca University of Hawai‘i at Mānoa EPSCoR Water Dynamics Workshop Burlington, VT 10 November 2008

2. Water, water, everywhere... Setting Extreme geographical isolation High water demand High inter-annual rainfall variability Prone to water shortage

3. Expectations and observations of warming shift attention to higher latitude land areas Source: AR4, IPCC (2007) 1920-2005 High-latitudes: +2.3 o C Tropics: +0.8 o C

4. Source: AR4, IPCC (2007) However, while land areas have warmed fastest at high latitudes, warming of the Pacific Ocean shows cyclical patterns with respect to latitude

5. Pacific Decadal Oscillation (PDO) Source: AR4, IPCC (2007); also see Mantua et al. (1997) and Power et al. (1999)

6. El Niño-Southern Oscillation (ENSO) Source: AR4, IPCC (2007); also see Trenberth and Caron (2000)

7. Hawai‘i Temperature Index GLOBAL TRENDS: 1906-2005: 0.074 o C per decade 1976-2005: 0.177 o C per decade Source: AR4, IPCC (2007) Source: Giambelluca et al. (2008)

8. HTI—PDO—SST PDO SST Source: Giambelluca et al. (2008)

9. Hot Nights Source: Giambelluca et al. (2008) 1975-2006 Trend ( o C per decade) Minimum Temperature Maximum Temperature All Stations0.275*0.054 Low-Elevation0.153*-0.007 High-Elevation0.441*0.085 *Significant at p = 0.5

10. Decrease in Day-Night Temperature Difference Source: Giambelluca et al. (2008)

11. Hawai‘i Rainfall: Long-Term Decrease Source: Chu and Chen (2005) Hawai‘i (winter) Rainfall Index (HRI)

12. Mean altitude ~2200 m (7200 ft) Frequency ~80% Stable atmospheric layer Forms a barrier to rising air Because rising air is the predominant means by which clouds form, cloud development is capped at the TWI level As a result, relatively thin clouds produce less precipitation when TWI is present Climate changes resulting in either more frequent or lower altitude TWI will cause a reduction in rainfall Trade-Wind Inversion

13. Effect of Inversion on Rainfall Source: Adapted from Tran (1995) HaleNet: Haleakalā Maui

14. Effect of Inversion on Rainfall Source: Adapted from Tran (1995) HaleNet: Haleakalā Maui

15. TWI Trends Source: Cao et al. (2007)

16. Warming and Ecosystem Services Asner et al. (in review)

17. Warming & Carbon Dynamics Native forest site currently a net carbon sink (2.8-3.4 Mg C ha -1 yr -1 ) Gross primary production controlled mainly by PAR Ecosystem respiration controlled by temperature Each 1ºC increase in temperature causes a 15% increase in respiration loss Warming may reduce competitiveness of native trees versus invasive trees

18. Species Invasion & Hydrological Services Species invasion is a major environmental problem in Hawai‘i Success of invasive trees may be facilitated by warming What secondary impacts do these trees have on hydrological services? Psidium cattleianum is the most widespread invasive tree in Hawaii

19. Field Sites Invaded Forest Site –‘ohia forest invaded by Psidium cattleianum (strawberry guava) Native Forest Site –Metrosideros polymorpha (‘ohia) –Cibotium spp. (hapu‘u; tree fern)

20. ET invaded 27% more than ET native ET Available Energy

21. SUMMARY Hawai‘i is highly vulnerable to and prone to water shortageHawai‘i is highly vulnerable to and prone to water shortage Tropical areas like Hawai‘i are subject to significant impacts of global warmingTropical areas like Hawai‘i are subject to significant impacts of global warming Trends suggest Hawai‘i is getting warmer and drierTrends suggest Hawai‘i is getting warmer and drier Warming will have negative impacts on native forests and favor invasive treesWarming will have negative impacts on native forests and favor invasive trees Invasive trees can significantly reduce water availabilityInvasive trees can significantly reduce water availability Findings suggest severe combined and synergistic effects of climate change and species invasion on Hawai‘i’s terrestrial ecosystems and their servicesFindings suggest severe combined and synergistic effects of climate change and species invasion on Hawai‘i’s terrestrial ecosystems and their services

22. THANK YOU thomas@hawaii.edu