Freeloaders of the forest

Observations on the differences between New Zealand and Australian forests (9 minute read)

The gum trees towering above me aren’t even close to Australia’s tallest, but I’m still awed by their height. A few trees in New Zealand achieve this stature, especially the mighty kauri and kahikatea, but I don’t expect to see these forest giants in their full glory in a suburban gully. In south-east Queensland, though, gum trees of extraordinary height can be found on roadsides and back gardens.

image credit: Melanie Newfield

I’m only 45 minutes' drive from the monstrosity that is Surfer’s Paradise, the heart of the Gold Coast. It’s a place I find fascinating, but not in a good way. There’s a maze of high-rise apartments and concrete fringing what seems to be a perfectly average Australian beach. There’s the massive motorway which carries huge volumes of traffic from one end of the coast to the other. There are canal communities, locked away behind walls and security gates, where every mansion has an expensive boat moored at its private dock. There are the theme parks, which are fun if you are partial to that kind of thing, but I’d prefer a botanical garden. South from Surfer’s Paradise, the high rises aren’t so high, and it’s still possible to glimpse what the place might have been like seventy years ago. Between the apartment blocks, there’s an occasional modest holiday house, perhaps from the 1950s. But this seems to be as far back as history goes in the area. It seems as if everything which went before has been obliterated.

The Gold Coast isn’t the kind of place I’d normally choose to visit, but I have family who live here and so I’ve come to see them. It means that I’m taking a closer look at areas where tourists don’t usually visit. What surprises me is how much forest survives there. I can’t tell if it’s original, because I don’t have enough knowledge of Australia’s environment to distinguish forest which has regenerated in recent decades from forest which has been here for thousands of years. But the forest I see is beautiful and diverse, and it allows me to indulge my obsession with Australia’s iconic tree, the gum tree or eucalypt.

Gum trees are found from one end of Australia to the other, in almost every environment except rainforest. Depending on which botanist you ask, there are anywhere between 700 and 950 species, almost all of them found only in Australia. They are an ancient group, with fossils dating back more than fifty million years. But it’s only in the last two million years that they have come to dominate in Australia and evolved the staggering number of species seen today. In comparison, New Zealand has only around 800 species of trees and shrubs in total.

When I was a child, living in Auckland, we had a number of gum trees growing in our garden, and I have many memories of them. There was one tree which had a stout branch which grew horizontally, and I can remember lying across this branch peeling away the bark. Many eucalypts shed their bark regularly, leaving branches and trunks which are cool and smooth to the touch. I remember stroking the branches and holding my cheek against them. Others have bark which is tough and resinous – we had another gum with beautiful blue-grey leaves and a deeply-furrowed trunk of the darkest brown. Yet another, covered with pink flowers in the middle of winter, used to be alive with tūī feeding on its abundant nectar.

But seeing gum trees in New Zealand is not the same as seeing them as part of the natural landscape in Australia. So, although my reason for visiting Australia is to visit family in Brisbane, the Gold Coast and Sydney, I’m taking this opportunity to learn about the Australian environment, particularly the forests and waterways.

One crucial difference between the New Zealand and Australian environments is the amount of rain. New Zealand’s forests are rainforests – dense, multi-layered forest with a closed canopy which is found in areas where rainfall is abundant. In contrast, in Australia there are only limited areas which are wet enough to have rainforest. Outside these limited areas, the forest canopy is much more open than any forest canopy in New Zealand. When I look up, I see as much sky as tree.

My first forest walk is in a fragment called the Kimberley Forest Reserve. As I walk along, there are several points where I can see houses through the trees, so this is not a remote area. I’m not yet familiar with individual species of gum, but I can tell from the bark that there are several different species here. Some have rough bark to the tips of the highest branches, others are smooth from the base of the tree. I touch the trees as I pass. Even with my eyes closed, I’d know a gum tree, by the texture of the bark and leaves, and of course their smell. I love the smell of gum trees.

image credit: Melanie Newfield

Another thing which fascinates me about the forest in Australia is the bird life. In New Zealand, there aren’t many native species you can hear unless there has been extensive predator control. Most of the birds found in cities and suburbs are introduced. But in Australia, native species are everywhere, raucous and assertive. There are a number which have adapted well to city living, including crows, magpies, mynas, ibises, rainbow lorikeets and brush turkeys. In the Kimberley Forest, I see a group of mynas harassing a brush turkey, dive-bombing and squawking at it. I also spotted a couple of kookaburra and some birds which had the shape of New Zealand’s piwakawaka or fantail, although  they were greyer. They were one of the few things I saw, apart from some of the weeds, which were similar to forest in New Zealand.

The track I followed in the Kimberley Forest ran down a gully, and in New Zealand I’d expect to see a stream there. In much drier Australia, though, the gully is dry for half of its course, even though it’s winter and there’s been a reasonable amount of rain. As I get further down, I start to see water, but it’s in patches and it’s stagnant. Once I reach a flat area, there’s moving water, but it’s still sluggish and murky. I can’t tell whether this is the natural state of the stream or whether it’s an effect of the urban environment, which changes both the quality and quantity of water.

It might be sluggish and stagnant, but the stream still shows a stunning reflection of the forest canopy (image credit: Melanie Newfield)

I stop on a bridge and watch the water beneath me. Once I’m still, I notice odd little dimples moving over the water’s surface. A closer inspection shows that they are insects, which I later identify as water striders. I also spot at least one fish. It’s not large enough, and I’m not close enough, to identify it. However, there’s only one introduced species I know of which is likely to be in this kind of habitat, the gambusia, and I can tell it isn’t that. So I hope that I’ve spotted a native species.

I can see two other differences between typical New Zealand forest and the forest in the Kimberley Reserve. The first is that there are different types of species here compared with New Zealand. So far, I’ve been in Australia for a week and half, and I’m yet to see a single coprosma. This shrub, whose scientific name literally means ‘smelling of poo’ making it the perfect plant for introducing children to botany, has numerous species in New Zealand. It’s found from one end of the country to the other. Once you know how to identify it, you realise it’s everywhere, in every forest fragment and popping up in many suburban gardens. I’ve also not seen anything I can identify as a tree daisy, another group which is important in New Zealand.

Below the canopy of a gum tree forest, many of the plants belong to a small number of botanical groups or families – the legumes, the proteas and the myrtles. Gum trees belong to the myrtle family, but there are many other kinds as well, including species related to New Zealand’s mānuka. The protea family is rare in New Zealand but is a particular feature of both Australia’s and South Africa’s flora, and includes many kinds of banksia. The legume family is worldwide and includes familiar foods such as peas and beans. Australia’s wattles or acacias belong to this family, and they are another very common feature of gum forest.

One of the most astounding things about Australia is its botanical diversity. New Zealand has around 2,000 species of native flowering plant. Australia has ten times that, although there are many more undescribed species so the exact number isn’t clear. Because Australia is so much larger, in terms of land area New Zealand is more botanically diverse. But the sheer number of species in Australia is something which leaves me dumbfounded every time I take a walk. There’s so much to see I don’t know where to look.

The diversity of Australian plants, and the fact they belong to different botanical groups from New Zealand plants, is not necessarily obvious to a non-botanist. But the other difference is apparent to any close observer of nature. The structure of the forest is different. New Zealand’s forest has a dense canopy layer, as I’ve mentioned, and it also has scattered trees which grow taller than the canopy, known as emergent trees. These emergent trees are often laden with botanical free-loaders, other plants growing in their branches. While a few may be vines which have stems snaking their way down to the ground, most of them grow entirely in the tree tops. Some blow there on the wind, but many of them have fruits which are eaten by birds. Below the canopy, there’s a subcanopy and shrub layer of shade-tolerant plants. The ground layer is thick with ferns and mosses, plants which thrive in low light and abundant moisture.

In this reserve, I don’t see any plants living entirely in the upper branches of the gums. The layer below the canopy, however, is much more diverse, as is the ground layer. Ferns are mostly close to the stream, lower down, where it’s wetter. Away from the stream, many of the plants have thick, leathery leaves, an adaptation to dry conditions.

One of the things I see that I’ve never noticed before is the wide range of vines. None of them are flowering, which makes them difficult to identify. However, I can tell by their growth forms that they belong to many different groups. Some have stems which cling tightly to the trunk, as if they are glued to the trees. Others have long vigorous shoots with spines. These grow upwards quickly, flop over, and hook themselves into whatever they land on. Some scramble – usually these ones are spiny too. Some have stems which twine. Some have tendrils, like a pea vine. At first, these tendrils grow straight, but as they get older they coil themselves up like springs. If they come into contact with another plant, they coil around it.

There’s not enough rain to support plants which live entirely among the branches. The vines need their roots in the ground, or they simply won’t get enough moisture. However, there is no shortage of forest freeloaders here, hitching a ride to the canopy on the trunk of a gum tree.