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The effects of climate change on wild rice

April 17, 2020 by Beckie Gaskill

During the recent Lakes and Rivers Convention, Peter David gave a presentation on wild rice and climate change. Wild rice, “Manoomin” as it is known, is culturally important to Native Americans and holds a very special significance to many. Its range is geographically small, with Wisconsin making up a good portion of that range. 

David stated there are two types of wild rice, the zizania aquatira, which is the southern variety and found along the Mississippi River in lower Wisconsin, and the zizania palustris, or northern variety, found here in the Northwoods. The northern variety has a much larger seed, making it more important for human food. 

Manoomin also has great ecological value. Value as a food source to geese and swans is very important. Trumpeter swans were reintroduced in the state and, David said, has a population of over 5,000 by 2017. He suspected that number was even higher currently. He told the group swans, as well as geese, feed on wild rice all summer long.

As with most plants, Manoomin prefers certain habitats over others. It is an annual plant, which is very important, as that makes its life cycle much more easy to disrupt. It prefers depth ranges of 0.5 to three feet with water that is not acidic or darkly stained. It also prefers an organic and mucky substrate. It requires gently flowing water that is low in sulfates and sulfides. 

David showed the group a graphic of the life cycle of wild rice. At the stage when the rice is floating, it is the most critical time, and the time when there is the most crop failure. This stage can be easily uprooted or drown by high water or current flowing too quickly. In recent years, there have been many more large weather events that can cause such a disturbance, which can be detrimental to wild rice.  

By the beginning of July, he said, the rice is usually standing and the biggest danger of being flooded out or uprooted is gone. This does not mean the plant is “in the clear,” at that point, however. It is a wind pollinated plant, giving it limited dispersion ability. It is also naturally high variable as far as growth. 

While it is not necessarily cyclical in nature, David said, there is what he called the “four year rule,” that is normally applied to Manoomin. In four years, it is not uncommon to have a bumper crop, a failed crop and two crops that are average. He provided many photographic examples of rice beds that looked drastically different from year to year. He also provided photographs at various times of the year, showing how incredibly different beds look at different times.

In the face of climate change, there are issues for Manoomin, he said. The growing season is becoming longer in general, which favors other vegetation. Wild rice has become adapted to live in the harsher northern climates. With changes in climate, there is sure to be a change in wild rice as well. 

Another potential impact of climate change is more abundant pest species. Here, too, with a longer warm season and a milder winter, over winter survival of pests is increased.  One of the pests that is the most detrimental to Manoomin is the rice worm, which is the larvae of a moth, David said. The larvae is laid in a rice grain. It consumes that grain and then moves on to eat other grains of rice.

Other stressors include aquatic invasive species such as curly leaf pondweed and Eurasian water milfoil. Those species have become more prolific in some areas, causing even greater headaches. In some waters, these invasives can become especially problematic, pushing out native species such as wild rice. David also cautioned attendees about the means used to fish invasive species in their waterbodies. 

Use of chemical pesticides on invasive species can also have a negative effect on many native species. If other control methods can be used, David said, it can often be best for all of the surrounding plants as well.

David spoke about flooding and the effects it has had on wild rice in some areas. He spoke about a flood in Minnesota, which has five to six times the wild rice Wisconsin has. He showed photographs of a flood in 2012 that devastated the wild rice crop. Four years later, there was another such event, which extended over to the Bad River area. In 2018, there was a 1,000 year storm event on Father’s Day, which completely blew out the rice crop in the Radigan Foliage in Douglas County. This would prove to be a complete and permanent loss. Flowages such as this one, he said, were created to deal with natural losses in wild rice populations. 

Another climate change-related stressor for Manoomin is disease. With warmer, humid conditions, brown spot disease, a fungal disease, has become more prevalent. 

For a species with so many stressors in the environment naturally, climate change will likely only worsen the plight.

Beckie Gaskill may be reached via email at [email protected]

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