Now we're on The Threatened Tree Trail (what an alliteration!). In this part of the Arboretum, you will find many endangered trees from around the world. They are transplanted here as a living specimen to preserve them—one important role of an arboretum.
Before knowing how threatened they are, let's get to some basics. How do we measure how threatened a tree is?
This classification has been mainly led by the International Union for Conservation of Nature (IUCN), which publishes the Red List of Threatened Species regularly. IUCN has many specialist groups which carry out literature review, field research, and expert consultation to evaluate how threatened any species is. They take into account many factors: number of mature (reproducing adults), the range size, the rate of declining, and more.
IUCN Red List is the current gold standard of threat classification, ranging from Extinct to Least Concern.
In this part of the Arboretum, you will find many threatened trees. Here is the list of them and let's see if you can find them all.
Threatened Trees at Harcourt Arboretum
One thing you may notice about these information boards are the animals on them. In fact, look at the table again. I bet you have heard more animals listed there than the trees. It is unsurprising. What's surprising is that these animals and trees are facing equal threats. You probably won't be able to touch a giant panda in your life, they are well protected, but you can definitely touch a coffin tree right in front of you. And giant panda is not even that threatened compared to many other trees on that list!
This leads to the question, why are we blind to plants and their sufferings?
All animals are equal, but some animals are more equal than others.
—— George Orwell, Animal Farm (1945)
Giant panda is the mascot of World Wide Fund for Nature, but it is not even an endangered species anymore.
Plant blindness is a well-observed cognitive bias than human tends to ignore plant species. This term was coined by the botanists and biology educators J. H. Wandersee and E. E. Schussler in 1999. There are two main factors of plant blindness: human biology and culture.
Human visual systems cannot effectively process all the information that in seen—a common phenomenon seen in animals known as sensory overload. (A good example otherwise will be fish schooling: fish swim in schools in front of predators, e.g. a shark. The shark will be indecisive which fish it should start with and at the end catch none of them.) Studies have shown that humans prioritise colours and movements—which are usually either food or threat to us, and plants don't usually fit these criteria. Another theory is that our instinct is to protect our offspring, and many 'adorable' animals look like our babies.
Uncanny valley is also an interesting way to think about why we are fond of animals. 'Adorable' animals such as pandas and bears usually resemble humans, and we tend to be more familiar with them.
Culture also plays an important role. Plant blindness is actually less prominent in some countries, especially indigenous communities where plants are highly valued for religion, medicine, and mythology (think about Chinese medicine!). However, in many societies, education has been zoo-centric.
<aside> 💡 Recall your high school education. Do you see more animals or plants from your biology textbook? Do you visit a zoo more or a botanic garden?
Maybe the best memorable example is the Ocean Park in Hong Kong. They integrated a zoo and an amusement park, which linked the joy and memory between the two.
</aside>
Giant redwood has an exceptionally large genome. They contain 6 sets of chromosomes (hexaploid) and make up a 27-Gb genome. Genome (our DNA) is made up of basic units called nucleotides, there are four: A, T, C, and G. A 27-Gb genome means that it can be decoded into 27,000,000,000 letters of A, T, C, and G. Humans, in contrast, only have two sets of chromosomes (diploid) and make up a 3-Gb genome.
While we are unsure why they need such a big genome, we at least know where it comes from. Before all conifers diversify, there was an ancient whole genome duplication around 400 million years ago. There were another round for all pines and conifers around 200 million years ago. After a genome duplication, sometimes part of the genome will be lost again in some species, but still many species retain a big genome.