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Meet the New Yard: Tropical Plants, Invasive Species and Drunken Trees
Alex Steffen, 31 Jul 07

When we look at ecosystem disruption and climate change, we have a great tendancy to focus on the really sexy aspects (by media standards) -- the melting of Greenland, the spread of the Sahara, the predicted extinction of rhinos, tigers and all sorts of other large critters. But some of the effects will land a lot closer to home.

Take, for instance, the change in gardening climates and the dramatic spread of invansive species. As the global climate changes, the impacts can be seen in what plants will thrive in our gardens, and already the mix of plants that will do well in any particular place is changing rapidly.

So rapidly that the (U.S.) National Arbor Day Foundation felt it necessary to update the Plant Hardiness Zones Map. That's the map that gardeners and farmers use to figure out what seeds to plant where they live. Their findings? That across huge swathes of the United States, climate zones have already shifted: according to James Hansen, such zones may already be marching northwards at a rate of tens of kilometers a year.

And, of course, climate change has only just begun. Most of us can expect to see climate conditions in our back yards which are warmer and different (wetter or drier at unusual times) than we're used to, with springs that come earlier and autumns that arrive later. As insect and bird breeding cycles fall out of sync, and as songbird populations plummet because of habitat loss, housecat predation and polution, we can expect some strange plagues of previously unnoticed insect pests. In some places, perhaps most places, we can expect an increase in "freak" weather events.

Then, too, because of both the disruption of native ecosystems (disturbed ecosystems are vulnerable) and climate change (which is disrupting ecosystems once thought relatively healthy, like the drunken trees falling over in Canada's boreal forest), a mounting wave of invasive species migrations are being seen all around the world. From pythons in the Everglades to voracious Tilapia in lake Victoria, plants, animals and microbes are spreading rapidly into niches in which they didn't evolve, often with disastrous results.

For one window on what that means for people who care about the places around them is Ceiridwen Terrill's excellent short book Unnatural Landscapes: Tracking Invasive Species. Terrill explores the work of "invasion ecologists" -- scientists who are studying the spread of non-native species and the possible restoration responses to that change -- are finding that not only climate change and local environmental carelessness, but larger forces as well are driving a biological blender effect, where plants and animals from various places are scattered all over the world:

Policymakers have not yet integrated the language of bioinvasion into their discussions of trade policies, and the negative consequences of invasion do not inform economic laws. [T]he expansion of global commerce without careful consideration of environmental impacts is shaping evolutionary processes in ways we cannot even foresee...

But while we certainly need a more thoughtful approach to the physical exchanges involved in global trade, that's not the only change we're capable of making. Indeed, Terrill has a whole chapter on the various ways people are coming together to preserve native species, from forming restoration groups to fighting the exotic pet trade. And there is much, much more most governments could do. In the U.S. a single biologist working for the federal government is responsible for judging whether government action against a particular species is warranted: needless to say, she can't keep up with the workload.

We ought instead to have a vigorous network of citizen-scientist/ professional scientist collaborations with aggressive regulatory action. Scientists point to Australia's system for screening new ornamental plant species as a better model for assessing the risks of introducing new species. Others are investigating new technologies for eliminating the use of ballast water or monitoring it for invasive species.

But ultimately, once again, it is our thinking that must change above all else. We are used to imagining the climate as a constant; we are used to imagining nature as inexhaustible; we are used to imagining biodiversity fixed to places -- we are used, in short, to imagining ourselves as small and nature as large and unchanging. Now we know this not to be the case. The daily operation of our society is changing the weather, remaking the landscape and redistributing the planet's living creatures... with potentially catastrophic consequences.

If we can take seriously our responsibility to transform our civilization, we can over time beat all these problems and restore health to the planet's ecosystems... and our own backyards. But the time to start is now.

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Nice post...a reminder that all things natural shouldn't be taken for granted. And, yes, we can make a difference, one tree at a time.

Posted by: Woodrow Nelson on 31 Jul 07

There's an interesting initiative that's been going on in NE Victoria for a decade or so, now. It is called the Regent Honeyeater Project and has had some remarkable successes in restoring the native vegetation to an area which was effectively clearfelled over a century ago.

Some interesting points wrt the issues raised in your post:

- plantings of local natives have a very high survival rate (> 90% after two years). This has held true even in the past year or two, when the region has suffered from severe drought conditions. One of the main reasons cited for the success rate is the care taken to choose seeds from local plants (not just native to the area but local to the region), and the care taken to plant seedlings according to the local conditions (soil type, drainage etc.) I don't know how close the area is to the limit of any 'hardiness zones'

- As the native trees become established, they draw out a lot of the water from the surrounding soil, which tends to suppress the invasive pasture weeds, and allows the native grasses to re-establish themselves.

Posted by: Tony Fisk on 31 Jul 07

I'm noticing a lot of change in my allotment in northern England. A lot of the blackberries are ripe already and the endless heavy rain has caused a lot of blight in the potato family. We also have a lot of problems with Japanese knotweed.

It's been a really tough year for food production. I'm trying out as great a variety of plants as I can manage and I'm trying to get it to work as a productive ecosystem but the goal posts keep moving.

I dread to think what will happen when food production gets seriously impacted globally.

Posted by: Joe Djemal on 2 Aug 07



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