Botanical Gardens & Plant Conservation

September 26, 2017

Botanical gardens are among my favorite places in the world. I find them both relaxing and stimulating, offering something for all of our senses. Botanical gardens are valuable for more than just their beauty. They serve a deeper purpose than simply showcasing endless poinsettia varieties or yet another collection of Dale Chihuly pieces (a phenomenon I can't quite wrap my head around). Botanical gardens are vitally important centers of ex situ plant conservation efforts.

Ex situ conservation literally means "off site conservation," when plants are grown within the confines of a botanical garden, often far away from their native habitats. This is an important process in and of its own because housing plants in different locations safeguards them from complete annihilation. Simply put, don't put all your endangered eggs in one basket.

I don't think botanical gardens get enough credit for their conservation efforts. Sadly, such endeavors are often overshadowed. That's not to say we don't have a good handle on what is going on. In fact, a study published in August of 2017 looked at the status of ex situ plant conservation efforts around the globe.

The paper outlines a conservative estimate of the diversity of plants found in botanical gardens and highlights areas in desperate need of improvement. Utilizing a dataset compiled by Botanic Gardens Conservation International (BGCI), the team found that the world's botanical gardens contain somewhere around 30% or 105,209 of the 350,699 plant species currently known to science. In total, they estimate humanities various living collections contain representatives from roughly 90% of the known plant families. That is pretty impressive considering the scale of plant diversity on our planet.

Proportions of the world's plants represented in botanical garden collections (Source)

Their research didn't stop there either. The team dove deeper into these numbers and found that there are some serious discrepancies in these estimates. For instance (and to my surprise), botanical gardens house more temperate plant species than they do tropical plant species. They estimated that nearly 60% of the world's temperate plant species are being grown in botanical gardens around the world but only 25% of tropical species. This is despite the fact that most of the world's plants are, in fact, tropical.

Similarly, only 5% of botanical garden collections are dedicated to non-vascular plants like mosses and liverworts. This is a shame not only because these plants are quite interesting and beautiful, but they also are descendants of the first plant lineages to make their way onto land. They are vital to understanding plant evolution as well as plant diversity.

Orchid conservation at the Atlanta Botanical Garden (learn more)

As I mentioned above, ex situ conservation efforts are critical in fighting plant extinctions across the globe. With 1/5 of the world's plants at risk of extinction, the authors of the paper were particularly interested in how botanical gardens were doing in this regard. They found that although various institutions are growing nearly half of all the known threatened plant species on this planet, only 10% of their collection space is devoted to these species. It goes without saying that this number needs to improve if we are to stave off further extinctions.

Taken together, this study paints an interesting and informative picture of botanical garden collections on a global scale. They are doing amazing work to protect and showcase plant diversity. However, there is always a need for improvement. More space and effort needs to be made in ex situ plant conservation efforts. More plants, especially little known tropical species, need to be brought into cultivation. More space must be devoted to propagating threatened and endangered species. Finally, more attention must be given to natural plant diversity rather than gaudy cultivars. If you love botanical gardens as much as I do, please support them. As the authors so eloquently summarize, "Without deep sustained public support, the plant conservation movement will struggle."

Pitcher's Thistle and the Dunes It Calls Home

June 26, 2017

Sand dunes are harsh habitats for any organism to make a living. They are hot, they are low in nutrients, water doesn't stick around for very long, and they can be incredibly unstable. Despite these obstacles, dunes around the world host rather unique floras comprised of plants well suited to these conditions. Sadly, we humans have been pretty good at destroying many of these dune habitats. This is especially true along the shores of the Great Lakes. To put this in perspective, I would like us to take a closer look at a special Great Lakes dune denizen.

Meet Pitcher's thistle (Cirsium pitcheri). It is a true dune plant and is endemic to the shores of the upper Great Lakes. Its a rather lanky plant, often looking as if it is having a hard time supporting its own weight. Despite its unkempt look, adult plants can reach heights of 3 feet, which is quite impressive given where it lives. It is covered in silvery hairs, giving the plant a shiny appearance. These hairs likely protect the plant from the onslaught of sun, abrasive wind-blown sand, and desiccation. One of the benefits of growing in such inhospitable places is that historically speaking, Pitcher's thistle could grow with little competition. Individual plants grow for roughly 5 to 8 years before flowering. After seeds are produced, the plant dies. The seedlings are then free to develop without being shaded out.

The last century or so have not been good to Pitcher's thistle. Shoreline development, altered disturbance regimes, and isolation of various populations have fragmented its range and reduced its genetic diversity. To make matters worse, its remaining habitat is still shrinking. Shoreline development has altered wave action that is vital to these dune habitats. Waves that once brought in new sediments and built dunes are largely carving away what's left. They are eroding at an alarming rate that even dune-adapted plants like Pitcher's thistle can't keep up with. Recreational use of these habitats adds another layer as heavy foot traffic carves deep scars into these dunes, furthering their demise.

One silver lining in all of this is that dedicated researchers are paying close attention to the natural history of this species. They have discovered some fascinating things that will help in the recovery of this special plant. For instance, it has been observed that although trampling doesn't necessarily kill Pitcher's thistle, it does damage sensitive buds. This often results in plants developing multiple flower heads. Although this sounds like a benefit, researchers discovered that these damaged plants actually produce fewer viable seeds despite producing more flowers.

Also, they have found that American goldfinches are playing a considerable role in its reproductive success. Despite the tightly clasping, spiny bracts that protect the seeds, goldfinches have been found to reduce seed production by 90% as they forage for food and the fluffy seed hairs for nest building. Evidence suggests that goldfinches are more likely to target small, isolated populations of Pitcher's thistle rather than large, contiguous patches. The reason for this is anyone's guess but it does suggest that they way around this issue is to supplement dwindling populations with new plants grown from seed.

Without intervention, it is very likely that Pitcher's thistle would go extinct in the near future. Luckily, researchers and federal officials are teaming up to make sure that doesn't happen. Long term population monitoring is in place throughout its range and a sandbox technique has been developed for germinating and growing up new individuals to supplement wild populations. Through habitat restoration efforts, supplementing of existing and the creation of new populations, the future of this charismatic dune thistle has gotten a little bit brighter. It isn't out of the metaphorical woods but there is reason for hope.

Photo Credit: [1]

Plight of the Panda: a bamboo story

December 24, 2015

Photo by Smithsonian's National Zoo licensed under CC BY-NC-ND 2.0

There are few creatures more iconic than the giant panda. These bears are the poster children for conservation movements around the world. Unlike their ursine relatives, pandas have abandoned carnivory for a diet that consists almost entirely of bamboo. In the light of human destruction, specialist lifestyles like the pandas are a risky strategy. It doesn't take much to upset such obligate relationships and humans are quite proficient at doing just that. However, the plight of the giant panda has just as much to do with the ecology of its food source as it does man-made destruction of its habitat.

Essentially giant grasses, the bamboo tribe consists of over 1,400 species worldwide. Not only are bamboo some of the tallest grasses in the world, they are also some of the fastest growing plants. Some have been known to grow 250 cm (90 in) in only 24 hours! As typical with grasses, bamboo can reproduce via underground rhizomes, forming dense stands of clones. Entire forests can be made up of the clones of only a few individuals.

The strangest part of bamboo ecology is that they rarely flower. A typical bamboo will live for 20 to 60 years before flowering, with some species taking well over 100 years. As such, bamboo experiences mast flowering events, with entire bamboo forests flowering all at once. After flowering and setting seed, the bamboo dies. Entire bamboo forests are lost in only a matter of weeks.

There have been many hypotheses put forth to explain this and while each has likely played a role in the evolution of this strategy, these mast flowering and subsequent death of bamboo forests probably serve to ensure the survival of the next generation. If the adults were to live through flowering and seed set, it is likely that the thick canopy of the parents would be too much for young seedlings to overcome. What's more, mass die offs create a significant fuel load for fires to sweep through. However catastrophic a fire may be, it reduces competition for bamboo seedlings.

Before humans fragmented their habitat, giant pandas had no trouble dealing with mass bamboo die offs. They simply migrated to a new bamboo forest. Anymore today, they cannot do that. When a bamboo forest flowers and dies, pandas in that area have nowhere to go. They simply starve to death. Because of this, pandas now occupy a mere fraction of their former range. What intact bamboo forests remain are restricted to the highlands of the Sichuan, Shaanxi, and Gansu provinces.

Despite considerable success in the captive breeding of pandas, there is simply not enough habitat to support their recovery in the wild. Because of this, captive breeding programs have come under harsh criticism. It has been argued that the massive amounts of money spent on captive breeding of pandas could be spent on habitat conservation projects elsewhere. No matter where you stand on the subject, there is no denying that pandas fall under the charismatic megafauna syndrome. They captivate the hearts and minds of people all over the globe. They also encourage the masses to open up their wallets. Sadly, it is probably too late giant pandas in the wild. If anything else, they certainly serve as a stark reminder of the importance of habitat conservation on a large scale.

Photo Credit: Abby Wood, Smithsonian's National Zoo (http://bit.ly/1qDX21K)