The long lives of wild orchids
When think about long-lived species, elephants and redwood trees may be among the first to come to mind, but what about orchids? Richard P. Shefferson from the University of Tokyo writes about terrestrial orchids’ long lives and their conservation.
Most people are probably aware that terrestrial orchids have beautiful flowers. However, few have the experience of following their long lives in the wild.
If you ever have this experience, then one thing that you will learn is that terrestrial orchids are not just perennials plants that can grow year after year, but that many are capable of living surprisingly long lives—often decades. I have been interested in the trajectory of these long lives since college. I got involved in my local community by helping a dedicated volunteer steward manage a gem of a local nature preserve named Grant Woods. I monitored the rare frogs, turtles, birds, and plants that lived in this unfarmed prairie remnant, and helped remove invasive plants such as common buckthorn and garlic mustard. It was through this experience that I also started monitoring the lives of rare plants, in particular the small yellow and white lady’s slipper orchids.
Like many orchids, these species have long lives and often seem to wink out of existence for a few years, only to come back later after having lived a completely subterranean life for those intervening years. This phenomenon, variously referred to as vegetative dormancy or prolonged dormancy, is one of my main subjects of study. Not only do these species have the potential for a long lifespan, but they also produce fruits full of thousands of dust seeds – embryos with seed coats, and little to no stored nutrition.
This combination of long lives and many seeds may make you believe that these plants may not need protection, but nothing could be further from the truth. Many orchids are under threat—due to their unique life cycles and growing human pressures.
Unfortunately, orchid seeds typically germinate at absurdly low rates in the wild. Most can only germinate under extremely limited conditions, such as the presence of an appropriate symbiotic soil fungus, and probably narrow pH and nutrient requirements, and even winter or spring temperature and precipitation. The result is that – left alone - wild populations tend to keep populations at the same numbers over long periods of time. They sometimes cycle through more productive and less productive periods, but never really expand. My own experience having monitored many orchid populations over the long-term in North America, Europe, and East Asia, is that orchid populations are probably typically declining slowly. In some cases, this decline is rapid, and often this is due to human interference. I have personally seen some populations go extinct, in the USA, France, Japan, Estonia, and China.
In Grant Woods, the long-lived lady slipper orchids that I first monitored are facing a series of converging human pressures: suburban development surrounding the preserve, changing local hydrology yielding saltier streams and groundwater (and the elimination of the calcareous soils that the lady’s slipper orchids need), the onset of earlier springs, the seeding of the soil with nitrogenous pollution from cars that favors certain plants over others, and the unstoppable steamroller of non-native plant invasion. These have all forced a strong volunteer management response to protect these orchid population and the surrounding remnant prairie community (indeed, remnant prairie is now so rare that without active management it will surely disappear as an ecosystem). Indeed, orchid populations in many parts of the world are in decline, as recent research has reinforced. Most remaining orchid populations that are not in decline probably exist only in large wilderness settings (though even these may be suffering from accelerated climate change).
Some of my more interesting research experiences with wild orchid populations have been in southern China, a place that I love to visit because of its wonderful people, amazing cuisine, and breathtaking nature. In southern China, orchids often only survive mostly on high, inaccessible peaks. This is not because of any unusual quirks in their life history, but because that is where they are least likely to be harvested. It was my experience, echoed by many colleagues, that populations found in more easily accessible areas disappear shortly after being found. Such disappearances usually happen because local farmers find them, harvest them, and sell them in the Chinese medicine trade.
Some populations may be able to sustain harvest for some amount of time, perhaps even a few years, because of the presence of a seed bank and some dormant adults. However, eventually such harvesting causes extinction, in some cases more quickly than others.
To be sure, there are a few orchid species that do not need much protection. Terrestrial orchids need our active help to survive throughout their long lives, unusual patterns of dormancy, and into the future