Wollemia nobilis (Wollemi pine).
Welwitschia in habitat.
Leaves of Gnetum gnemon.
Interview for Amazing Trees
This is the text of an interview I had with Mary Townsend, editor of the webzine Amazing Trees (now defunct). I have posted the full interview here for archival purposes.
Mary Townsend: [have lost the question!]
Me: You know Mary, Wollemi Pines are not the rarest of gymnosperms, nor even of conifers. About 350 of the roughly 650 species of conifers are treated as rare or endangered, as are essentially all of the 150 or so species of cycads. The ginkgo, one of the strangest of all trees, does not even exist in the wild; while the utterly bizarre Welwitchia is restricted to a small area in the Namib desert. The Florida Torreya is as rare as Wollemia (about 20 wild plants), but none are sexually mature. Only one plant of the cycad Encephalartos woodii has ever been found, and it was dug up and planted in several botanical gardens. At least one species of fir has never been found in the wild.
Mary Townsend: I've seen a photo of Welwitschia - it reminded me of a clump of bull kelp sitting in the middle of the desert! Is has cones, but surely it's not classed as a conifer?
Me: "Gymnosperms" includes four groups, usually called Orders or Classes in the taxonomic hierarchy. The conifers and cycads are fairly familiar groups. The third group has only one living species, the ginkgo, although many more species are known from the fossil record. The fourth group is called the Gnetophytes, and it includes three very different plant families. One is the Ephedras, also called joint-fir or (in North America) Mormon Tea. Their foliage contains the drug ephedrine, a stimulant and antihistamine found in many allergy and cold remedies. They are shrubs of arid regions with tiny cones a few millimeters long. The second group are members of the genus Gnetum, and these are so obscure that they do not have common names. Most of the 30 or so species are woody vines that live in wet tropical rainforests. Their "cones" look like berries, and only close anatomical study reveals them as gymnosperms. The third group consists solely of the species Welwitschia mirabilis, called Tumbo in South Africa (Namibia), where it is native. It is surely one of the strangest plants in the world. It has only two leaves, which grow constantly and live for hundreds of years, whipped into tatters by the ceaseless winds that blow across the Namibian desert. Although it may go for years without experiencing rainfall in its desert home, the plant actually has fairly low tolerance to drought and survives because of the coastal fogs that almost daily roll in off the adjacent Atlantic ocean. Its "cones" are borne on much-branched, woody stalks that arise from between the two leaves. There are many other bizarre anatomical features of Welwitschia that are too complex to explain without using some very obscure language, so let us leave it at this: the Tumbo is one weird plant.
Mary Townsend: You refer to the Ginkgo as "the strangest of all trees", is that because it's just so primitive?
Me: I say that because the ginkgo is absolutely unique. Every other tree that you might name, I can say, well such-and-such is a relative of it, and it belongs to such-and-such a group. You see, all of the other trees have context. But the ginkgo doesn't. All of its context, all of the other related trees, exist only as stone fossils. It doesn't even have the context of habitat, because it is almost the only tree I know of that is not known to occur in the wild (there are a few others, for instance a species of morning glory represented by a single tree in a village square in Peru). So, although the ginkgo is not a particularly unusual tree in terms of its appearance, it is very unusual in that it really doesn't fit in with any other living species.
Mary Townsend: I seem to remember a few years ago research was going on into an anti-cancer drug called taxine, which was developed from the Pacific Yew (Taxus brevifolia), and there was concern at the time that harvesting bark from the trees would not be sustainable. But I don't know much about the Florida Torreya, why is it so rare?
Me: First, I'd like to note that there was real concern for a few years that all the Pacific Yew trees would be killed for their taxol, but fortunately there are now plantations dedicated to growing yews for that purpose and the threat seems to have disappeared. The Florida Torreya is another story. As with many species of conifers, it has a relict distribution, meaning that it probably was widespread long ago but in recorded history has been confined to a very limited range and a highly specialized habitat. In Torreya's case, that habitat was wet ravines along a 30-km-long stretch of the Appalachiola River in Florida. Most of the area was occupied by pine forests, which periodically (every 20-100 years) burned up, but the Torreya avoided these fires by living in damp ravines, analogous to the fern gullies of the Blue Mountains. The fires opened up the habitat to air and sun, though, and perhaps this provided opportunities for the plant to disperse and establish new trees. However, for most of historic time, humans have tried to prevent those periodic fires and in fact the ecosystem has been fairly free of fire for a century or more. The Torreyas are being killed by a fungal disease, and it is thought (with the disclaimer that not a lot of work has been done on this problem) that the suppression of fire has contributed to the spread of this fungal disease, with such devastating effect that no sexually mature Torreyas are known to occur in the wild. Fortunately, the tree has ornamental value and as such is grown throughout the southeast United States, so it is not in immediate danger of extinction. However, it is certainly in danger of losing a large fraction of the total species genetic diversity, and that is a recipe for calamity at some later time. Various concerned agencies are trying to help the Torreya to survive in the wild, but it seems likely that achieving this goal will require reintroducing fire to an ecosystem where public sentiment is strongly opposed to fire. It is a bit like trying to sell bush fires as an ecologically sensible idea to residents of Sydney suburbs.
Mary Townsend: What would you say is the rarest conifer? What criteria do you use?
Me: Well, we've already named some great candidates. Ginkgo, which is unknown in the wild although thriving in cultivation. Florida torreya would probably be extinct in the wild by now, but for human intervention (although humans have also been responsible for the fire suppression...). There's a fir, Abies beshanzuensis, of which only 3 individuals were known to be living in the wild as of 1988. They live on a mountain in Zhejiang province, in eastern China. Another fir, Abies chengii, has been described from trees growing in cultivation in Great Britain. Its wild distribution is unknown; it was grown from seeds brought back by a collector in 1931, from somewhere in northern Yunnan, China. There's a cycad, Encephalartos woodii, that is only known from a single male plant found in the wild nearly a hundred years ago. It was cut up and transplanted to several botanical gardens, and is now found only in the collections of a few botanical gardens and at most a few hundred private collectors. Really, though, its practically impossible to say, "this is the rarest one." In 1993 Aljos Farjon and colleagues published "A preliminary world list of threatened conifer taxa." It includes 362 species, meaning that over half of the known conifers are threatened, and given the accelerating pace of Third World deforestation it's safe to say that the situation has measurably worsened since 1993. The cycads are a group characterized by relict distributions, and easily 85 percent of the 150 or so cycad species can be classified as threatened. Nobody has even looked at Gnetum, but since it mostly lives in tropical rainforests, it is safe to say that many of those species probably have a gloomy future. Taken as a whole, the gymnosperms are a group that cries out for formal protection. Fortunately, some progress is being made in that direction. Many countries try to protect species that are listed by CITES (the Convention on International Trade in Endangered Species), such as all the cycads, while many countries also respect listings by the IUCN (the World Conservation Union), which is expected to issue a revised list of threatened conifer taxa later this year. All threatened species in the United States, and in most other developed countries, have received some level of formal protection. However, the vast majority of species occur in Third World countries that do not have the resources, even when they do have the inclination, to protect little-known and economically unimportant plant species. I cannot yet name a gymnosperm known to have become extinct as a consequence of human actions, but I fear I will not be able to say that for very much longer.
Mary Townsend: I imagine conifers would be interesting to Dendrochronologists, because some of them are just so old!
Me: Well, this is one of the main reasons why I'm into this whole thing. I like studying organisms that live for hundreds to thousands of years and that are good enough to provide fairly detailed biographical information. Some people love these trees because they get so bloody BIG. I'm going to California in a few days with a friend, "Big Tree" Bob Van Pelt, who is utterly devoted to this idea and has found many of the largest known trees (watch my website for a report on this trip). I love them more because they get so OLD. The bristlecone pine (Pinus longaeva) gets to be over 5000 years old. The alerce (Fitzroya cupressoides) tops 3500 years. The giant sequoia (Sequoiadendron giganteum) tops 3000 years, while ages of over 2000 years have been attributed to limber pine (Pinus flexilis), yew (Taxus baccata), Alaska yellow-cedar (Cupressus nootkatensis), Rocky Mountain bristlecone pine (Pinus aristata), western juniper (Juniperus occidentalis), and even our old friend Welwitschia. Check out the "Topics" section of my website for a lot more discussion of tree ages!
Mary Townsend: I know that Dendrochronologists study tree rings, and that way you can work out the age of trees. But is it correct to say that there in the rings of trees is an accurate record of the climate of the earth, and that you can pinpoint events like volcanoes, floods, etc.?
Me: It gets kind of complicated here. I can say this much:
Mary Townsend: Is it possible to study tree rings without cutting the tree down? I know that scientists take cores from brain coral, and can find out a great deal about climate, etc., without damaging the coral.
Me: I wonder how you know that... in 1984, when I was studying at the Laboratory of Tree-Ring Research in Arizona, we had a visiting scientist from Townsville who came specifically to learn techniques for interpreting coral records. Anyway, yes, trees can be sampled using a device called an increment borer that extracts a core from the tree, about 4 mm in diameter and usually up to 500 mm long, although longer borers are sometimes used. Such a device causes negligible damage to a mature tree, which is used to having its bark drilled by insects all the time. A lot of dendrochronology, though, involves sampling dead trees, where saws or other invasive sampling techniques may be perfectly acceptable.
Mary Townsend: And how did you become so interested in Gymnosperms in the first place, and why take on the mammoth task of setting up the database?
Me: Well, as I say, I like big and old trees, and particularly because I live in western North America (where you can find what are probably the most impressive forests on the planet), I quickly noticed that most of the really impressive trees were conifers. So, about 10 years ago, I started trying to find out more about conifers as a whole, to try to learn more about why these trees were so extraordinary. It's a context thing, again. It struck me that since there are only about 650 species of conifers, it was logistically possible to name and describe and try to understand the ecology of each and every one of them, a task that would be impossible for most large taxonomic groups (for example, there are about as many trees in the genus Eucalyptus as there are in all of the Gymnosperms put together). As I worked on this task, initially in a very intermittent fashion, it quickly became apparent that the data were best organized in a hypertext environment, and a few years later hypertext became universally available in the form of HTML. The fact that this also meant the database could be posted on the Web was almost incidental; at the time, I thought that what I was doing was so hopelessly esoteric that essentially no-one would be interested in it. About a year ago, I went ahead with a Web presence. I must say, it's been an education. First of all, it really IS hopelessly esoteric, but the Web is so big that the site still gets about a thousand hits a month. Secondly, I've gotten a really interesting response. Most of my e-mail on the site comes from overseas. I get letters from teachers about what a useful teaching tool it is. Students tell me it's a great research tool for writing their papers. Scientists write and tell me all sorts of (you guessed it) hopelessly esoteric things that I then put in the database. Agency people write with technical questions. Gardeners write and ask about problems with growing their plants. Some people tell me stories about their experiences with particular species. Others want to know where they can learn more. And occasionally, media people have lots of questions. Basically, the database is turning into more than I ever expected it to, developing a life of its own, and I take care of it because I don't want it to die. It has a future. It will be interesting to see what that future is. And this is all so much more than I ever expected of a large number of ones and zeros.
Last Modified 2023-12-16
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