Between Food and Climate Change
By Glenn I. Teves, UH CTAHR County Extension Agent
Characteristics of climate change include weather extremes — very hot and very cold — as well as violent storms. We’ve seen it this year with one of the coldest winters in decades, record high summer temperatures, and more than our share of threatening storms.
One of the positive aspects of a cold winter was a bumper crop of lychee, a native to South China. Most of the older lychee varieties, including Kwai Mi, Hak Ip, and No Mai Tze require colder weather to flower than is normally found in Hawaii, while the newer ones such as Kaimana and Groff require less of a cold snap to trigger flowering.
The summer heat, on the other hand, has had a negative impact on many crops. Plants are affected by heat stress much like us, and warm nights can also cause problems when plants are unable to rest and recover from a hot day. Lettuce prefers a warm day with cool nights, and under high temperatures in the 90s, plants “hyperventilate” and cannot take up sufficient water and nutrients to supply its needs. Sensing they’re about to die, they will flower prematurely or “bolt.”
Important nutrients such as calcium require water to move to the growing tips of plants, so when a water shortage occurs, they will sacrifice the youngest parts of the plant to save the rest. The result is tip burn of the youngest leaves. Occationally we see imported romaine lettuce in the market with early tip burn along leaf edges.
A similar condition occurs on tomatoes in which flowers and young fruits will drop off. Under extreme conditions, the bottom of maturing fruits will turn black, referred to as blossom-end rot, rendering them unsaleable. Plants are growing so fast and cannot take up sufficient water and nutrients to supply it demand, especially calcium. In order to save the plant, it will sacrifice the youngest fruits. Under heavy rains and hot humid conditions, plants will take up water quickly, causing fruits to crack, and render them unsalable.
Taro prefers tropical conditions found in cool wet valleys. Under high temperature conditions, plants cannot take up sufficient water and nutrients while growing rapidly, and will rely on stored starches or carbohydrates from corms to survive. The result is a depletion of starches and gums resulting in poor quality taro, and a reversion of starches to sugar in a condition called “loliloli.” Poi made from this taro will be watery, sweet, and will sometimes rot instead of fermenting or souring properly, especially when grown under dryland conditions.
Some plant species can be conditioned to perform better in extreme conditions, this starts by selecting the right variety. Having varieties with large scavenging root systems helps, for example, but how you manage a crop is important. You can either give plants all they need and baby them, or condition them to get ready for hard times early in their life so they can survive.
Giving them too much of everything is called “luxury consumption,” so in lean times many of them cannot adjust. Utilizing these tendencies to benefit plants starts with tough love. These are some of the challenges of climate change, and some states are in the midst of these dilemmas. Are we ready for the challenge?