A lot has been made of the current shortage of poi in Hawaii. Actually, what is meant is the shortage of taro (Hawaiian: kalo) which is due to multiple causes: shortages of water and labor, as well as the apple snail infestation.
I've heard numerous Hawaiian activists mention the shortage of taro as contributory to the decline in the cummulative health of the Hawaiian community. Without taro to make poi with, Hawaiians turn to less-nutritious alternative foods to occupy the place in their diets once held by poi. These alternatives are potatoes and (more commonly) white rice. Neither rice or potatoes have the nutritional content of taro and neither is a traditional Hawaiian food. Poi was once the chief staple of the Hawaiian diet and its removal or decline in overall consumption removes a link to Hawaiians' historic culture. This is often taken as a sign that Hawaiians are "losing their culture" in the Great American Melting Pot.
But, is something being overlooked? Are there similar foods that ancient Hawaiians ate if/when the taro crop might fail for some reason? If a region's taro crop was destroyed somehow, were there no other foods indigenous to Ancient Hawaii that the people could eat until the taro crop recovered the following season?
Actually, there was and there still is.
While taro was the central staple of the Hawaiian diet, it wasn't the only food available and it wasn't even the most nutritious part of their diet. That place is held by the sweet potato. In Ancient Hawaii, two crops were planted more than any other: taro and sweet potato. Since taro that is used for poi is water-intensive, sweet potato would be planted in areas when water was not plentiful. The sweet potato doesn't require nearly as much water and could be harvested much more frequently. I understand that the people of Niihau would make a poi-like food using sweet potato, in lieu of taro, due to the scarcity of water on their island.
Essentially, poi is simply a root vegetable pounded into a paste, mixed with water and salt, allowed to ferment for a short time and then eaten. This is a very common form of food preparation found all over the world. Mashed potatoes are commonly served in American homes and restaurants, while mashed yams are commonly eaten in West Africa and this food is known by a variety of names, including fufu.
Ancient Hawaiians grew a number of foods that are still commonly available today that could fill the void left by taro: sweet potato, yams and breadfruit. All of these foods are grown in Hawaii and all are as nutritious as taro. In fact, sweet potato and yams are even better for than taro. Mashed breadfruit was used as either an augmentation or a substitute for taro and poi made from breadfruit was call poi ʻulu. It is my understanding that Hawaiians didn't make poi from yams, due to the texture of the food, which is rather gritty.
Certainly, poi made from yams (if you want to try it), sweet potato or breadfruit will taste differently than that made from taro and it will feel different when you eat it. But, any one of these three food can be used in place of taro in the Hawaiian diet and any of them is better for you than white rice.
Bear in mind that I am not substituting a non-native food to take the place of taro. I am simply advocating that Hawaiians adopt a practise that was done by their ancestors.