Washington People: Tiffany Knight

Knight of the Kingdom Plantae
By Diana Lutz

Tiffany Knight, PhD, associate professor of biology and director of the Environmental Studies Program in Arts & Sciences, with Leucaena leucocephala in Hawaii. Hawaii is one of the most biologically diverse regions on the planet, home to many endemic species, but this tree is not one of them. Indigenous to Central America, in Hawaii it is an agressively invasive plant that crowds out natives, 800 of which have been listed as endangered. Hawaiians call it koa haole, haole being slang for a foreigner or non-Polynesian resident of Hawaii.

Tiffany Knight sometimes mentions Melicope quadrangularis in presentations about her conservation work. This flowering shrub, which is endemic to Hawaii, was listed as endangered in 1994, 20 years after the Smithsonian Institution first petitioned to have it listed. Unfortunately, that was also two years after it became extinct.

It was a case of too little too late.

Knight, PhD, associate professor of biology and director of the Environmental Studies Program in Arts & Sciences at Washington University in St. Louis, has devoted her career to making sure enough is done on time.

This year, she is on sabbatical in Hawaii working to pull some of its many endangered plant species back from the brink. When she’s not at the desk writing about rare species, she’s in the field trying to figure out whether Hawaii’s most common tree is also in decline.

Most people I know don’t actually see plants except as background greenery. Do you remember when you started to really see them?

Studying sand-dune plants in the Florida panhandle as a 19-year-old undergraduate. That summer, I realized how important plants are to the stability and function of ecosystems because a hurricane swept through and dunes with plant communities that included native grasses with deep roots weathered the storm instead of eroding before it.

I know you’ve studied rare plants in Missouri and California. How did you get to Hawaii?

About once a year I do a weeklong workshop for the Center for Plant Conservation where I teach people from agencies like the National Park Service how to use matrix population models to devise effective management plans for endangered species. Matrix population models allow you to calculate population trajectories based on short-term observations of birth and death rates.

Five years ago, I was asked to do a workshop in Honolulu. I thought, ‘Great! I’d love to go to Honolulu. I haven’t been to Hawaii since my honeymoon.’

Once I got there, I was surprised to see that most of the people in the audience were from the Department of Defense. They have a huge presence in Hawaii. But I didn’t realize how much work they’re doing in plant conservation.

They have a 100,000-acre site on the Big Island called Pohakuloa. The Army says that soldiers who train there are more likely to survive in Afghanistan, so Pohakuloa is very important to them.

Their first priority is training, and they don’t hide that. But the Army doesn’t see any reason why they can’t do really good training and be good stewards of the land they’re using as well.

I’ve been consulting with them for years now, mostly for free, because what they’re working on is so interesting. They are stewards to about 60 species of rare and endangered plants, some of which are found nowhere else.

Is that just accident?


A Hawaiian kīpuka, an island of greenery in a sea of lava, often harbors rare species.

Army land is actually in better shape than some of the surrounding landscapes. Much of the land surrounding Pohakuloa has been developed for cattle grazing, and grazing is a lot harder on plants than Army training exercises.

Also endangered plants tend to be clustered on kīpukas, which are high spots lava flows later bypassed without covering. So the Army has roped off a lot of  kīpukas and other spots the plants seem to like. They’ve said we’ll save these for conservation; we won’t train there.

Then they focus intense conservation efforts on those locations. They build fences on top of volcanic rock to prevent non-native pigs and goats from harming the plants, and they go to great lengths to remove exotic grasses that outcompete the rare plants and are a fire hazard. 

What else are they doing?

Nursery-grown Schiedea kaalae being helicoptered in by the Army to establish a second population of this endangered species.

They’re also helping to establish new populations of endangered plants. Many endangered plant species are found in only one or two spots, which means a chance event could easily wipe them out. To prevent this, managers often try to establish “outplantings,” new populations of a plant at a distance from the other populations.

The Army does pretty amazing stuff to get plants to the right sites. On Oahu, for example, we found a site that we thought would be a good growing site for Schiedea kaalae. The trouble was it was basically on top of a volcanic mountain. The Army grew the plants in a greenhouse and helicoptered them in, so that they could be planted at the site.

What plant are you studying now?

I usually focus on rare species, but now I’m looking at the most common tree in Hawaii. Its scientific name is Metrosideros polymorpha, but its Hawaiian name is Ohia. It’s a beautiful tree that sets bright red flowers, and it’s found on the Hawaiian islands and nowhere else.

On the islands it makes up about 40 percent of the tree biomass, so it’s really common. It’s called polymorpha, which means shape-shifter, because it’s so variable. It can grow almost anywhere, and it looks very different depending on where it’s growing. But it’s the same species all over the place.

This species has great ecological and cultural importance to Hawaii. It may be declining across all six islands, but we aren’t sure yet what is actually happening because the decline may be part of a natural cycle.

I am spending part of my sabbatical doing basic demographic studies on Ohia populations, just trying to figure out whether populations are declining, and, if so, what’s replacing them, and what the consequences of replacement will be for ecosystem health, so, very simple stuff that I hope will set the stage for future research.

When it grows in bogs, the Hawaiian Ohia may mature and flower when it is only a few inches tall. In other habitats, it may grow to towering heights. Not for nothing is it called polymorphic.

You have a young son. Have you ever thought of writing a children’s book about what you do?

My son’s favorite book right now is the classic The Very Hungry Caterpillar. Perhaps he is showing an early interest in plant-animal interactions.

For now, I am enjoying the books that are out there, but, perhaps, as my son gets older, I will find an empty niche I could help fill and I will write a book.

Diana Lutz
Senior News Director, Science
(314) 935-5272
Tiffany Knight
Associate Professor of Biology in Arts & Sciences
(314) 935-8282