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Thomas Giambelluca University of Hawai‘i at Mānoa

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. Water, water, everywhere. Setting

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Thomas Giambelluca University of Hawai‘i at Mānoa

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  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 High-latitudes: +2.3oC 1920-2005 Tropics: +0.8oC 1920-2005 Source: AR4, IPCC (2007)

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

  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: 0.074oC per decade 1976-2005: 0.177oC 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 *Significant at p = 0.5 Source: Giambelluca et al. (2008)

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

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

  12. Trade-Wind Inversion • 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

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

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

  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. ETinvaded 27% more than ETnative ET Available Energy

  21. SUMMARY • Hawai‘i is highly vulnerable to and prone to water shortage • Tropical areas like Hawai‘i are subject to significant impacts of global warming • Trends suggest Hawai‘i is getting warmer and drier • Warming will have negative impacts on native forests and favor invasive trees • Invasive 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 services

  22. THANK YOU thomas@hawaii.edu

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