Save Our Native Plants

Tim Johnson, director of Smith’s botanic garden, doesn’t mince words when it comes to the importance of plant biodiversity and our very survival: “No matter how powerful our internet, no matter how smart our cellphones, no matter how fast our airplanes, everything that we have depends on healthy ecosystems—everything.” 

Before he came to Smith in 2017, Johnson was head of preservation at Seed Savers Exchange, an international nonprofit organization that conserves, shares and promotes heirloom seeds and plants. At Smith, he is involved in a number of projects to restore and retain biodiversity on campus, including a fledgling germination program that has enormous implications for protecting the biodiversity of plant life in the Northeastern United States. 

Biodiversity, Johnson explains, is the biological diversity of a population or a species. For scientists, “it’s a measure of how much difference exists.” Here he talks about diversity of plant life and its role in climate change adaptability. 

PLANTS ARE THE FOUNDATION 

“Everything we have is directly or indirectly dependent on plants. The fuel we use, the materials we build with, the rare-earth metals that we need to build batteries and cellphones—we can’t run the machines to do that without the petroleum products that come from decomposed plant life. Everything we have, we owe to plants.” 

BANKING ON THE FUTURE 

“Seed banking is an important tool for preserving genetic diversity in the face of climate change and human-caused habitat loss. We’re exploring projects with the Native Plant Trust seed bank, which is a large regional seed bank of New England plants, to put students on the front lines of regional conservation efforts. We also collect and share seeds from our collections with other botanical gardens. Students do much of the work collecting, cleaning and sending out seeds from a wide range of species, so it’s a learning tool for helping students understand the importance of biodiversity.” 

EXISTENTIAL THREATS 

“Humans are the No. 1 reason we’re losing diversity. The ecosystems of forests, for example, are resistant and resilient to a certain level of disturbance. But if we clear-cut those forests, where are the seeds going to come from that allow the ecosystem to bounce back? We’re seeing both primary and secondary threats by humans. Primary is turning forests into land for agriculture, housing developments or shopping malls. Secondary are the effects from what we have done to cause climate change. In our region, for example, it’s getting really hard to grow sugar maples on campus because our winters aren’t producing as much snow, which results in deeper freezes that are killing the roots of our sugar maples.” 

HELPING PLANTS GROW 

“Our seed germination lab is up and running. We are studying seed physiology—what mechanisms, hormones and environmental conditions promote or prevent germination of native species—so they can be reliably germinated. With the support of a Stanley Smith Horticultural Trust grant, student researchers have been looking at bearberry (Arctostaphylos uva-ursi), sweet fern (Comptonia peregrina) and Pennsylvania sedge (Carex pensylvanica). These are most often propagated by cuttings. If we can figure out how to reliably germinate them, it opens the door to using more local and genetically diverse materials in the landscape.” 

BIODIVERSITY EFFORTS ON CAMPUS 

“One of the big things the college is doing is controlling invasive species around Paradise Pond, as these tend to form a monoculture that crowds out our native species. If we take out the invasives and keep them out, we hope the native ecosystem can come back and, with some help, regain and hold that ground. We’ve also taken steps to prevent new introductions by not planting known invasive species.” 

A SURVIVAL STRATEGY 

“Two things that are really important to understand when talking about biodiversity are the concepts of resistance and resilience. Resistance is the ability of an ecosystem to resist a change or disturbance—fire, more rain, less rain, an invasive species moving in. Resilience is the ability of an ecosystem to bounce back after a disturbance. The bigger the mosaic of genetic diversity within a population or a species, the more likely—when some change does happen—some of the individuals will survive.” 

NO DIVERSITY, NO RESILIENCE 

“When an invasive is able to dominate or take over an ecosystem, it can change that ecosystem to favor the invader to the detriment of ecosystem function. We don’t have the resistance and the resilience that we once had because there’s no diversity.” 

LESSON OF THE MELALEUCA TREE 

“In Florida, the Melaleuca tree was brought in from Australia to assist sugarcane and citrus growers in the 1900s. This species’ high rate of transpiration means that trees pull water from the soil and throw it up into the atmosphere fast enough to dry out swampland. But it also forms dense clusters where nothing else can grow; it monopolizes the soil, and the trees produce a large amount of volatile compounds, making these stands highly flammable. In the event of a fire, any other species that are nearby are wiped out and only the Melaleuca is able to recolonize.” 

INVASIVES AND CLIMATE CHAOS 

“Because of the globalization of moving plants out of their native regions, invasive species have moved in. These invasives seem to be able to take advantage of the chaos that climate change is causing. So, they do better than the native species if the weather is colder or wetter or warmer or drier than usual. We’re just starting to learn about how they do it and some of the tricks that they’re using. For instance, they may leaf out sooner in the spring, so they capture more sunlight and shade out native seedlings and plants; they may stay in leaf later, so they store more energy and produce more seed; or they may produce fruits that are more attractive to birds and get spread around more readily.” 

This story appears in the Spring 2020 issue of the Smith Alumnae Quarterly.

Photograph by Jessica Scranton