Islands Under Pressure
Goal: After this lesson you can explain why climate change is an unusually sharp threat to kava and the islands that grow it. Subject: Geography | Run time: about 6 minutes
Quick recall
Last time we learned why kava needs volcanic soil. Two quick questions. One: which three minerals boost kava's compounds? Potassium, magnesium, and iron (Lebot et al., 1992). Two: why can a coral atoll not grow kava? Its soil is too shallow and mineral-poor (Lebot et al., 1992).
Why this matters
Kava's geography, a small set of tropical volcanic islands, is also its weakness. The same islands that make the perfect kava bed are some of the places most exposed to a changing climate. When the ocean that protects kava starts to rise, it does not just threaten the crop. It threatens the islands themselves.
The idea
Walk through the threats. First, heat. Kava likes warmth up to the mid-80s Fahrenheit, but as average temperatures climb a few more degrees, days that push past 90 bring heat stress to the plant (Lebot et al., 1992). Second, rain. Kava needs steady, even rainfall, and a shifting climate brings it in the wrong amounts, drought one season and flood the next. Then come the threats that are unique to islands. As the sea rises a foot or two, low coastal growing land is lost outright, and salt water pushes into the island's freshwater, the thin layer of rainwater that floats on top of the saltwater in an island aquifer, called the freshwater lens (Lebot et al., 1992). Salt in that water is poison to kava. And stronger tropical storms, pushed from category three or four toward category four or five, can flatten a kava garden in a night. Put it together and kava is a warning sign. It grows only on small tropical islands, and those islands are on the front line of climate change. Protecting kava and protecting these island nations turn out to be the same task.
Picture it
Picture a low shoreline kava garden on a Pacific island. Now picture the sea creeping up the sand, year by year, and salt seeping into the soil from below. The plants nearest the water yellow and die first. Behind them, a stronger storm season tears at the rest. The garden is being squeezed from below by salt and from above by wind.
Remember this
The fact to carry out: kava grows only on small tropical volcanic islands, which makes it sharply exposed to heat, shifting rain, sea-level rise that salts the freshwater lens, and stronger storms (Lebot et al., 1992). Kava's fate and the fate of these island nations are tied together.
Quick check
Quick check. Name one island-specific climate threat to kava. Either sea-level rise salting the freshwater lens, or stronger tropical storms destroying crops (Lebot et al., 1992).
Key Takeaways
- Rising temperatures bring heat stress to kava on days above about 90 degrees Fahrenheit (Lebot et al., 1992).
- Sea-level rise floods low growing land and pushes salt water into the island freshwater lens, which kava cannot tolerate (Lebot et al., 1992).
- Stronger tropical storms can destroy kava gardens (Lebot et al., 1992).
- Kava's island geography makes it an early warning sign of climate pressure on Pacific island nations.
Sources
- Lebot, V., Merlin, M., & Lindstrom, L. (1992). Kava: The Pacific elixir. Yale University Press.