First off to Skr only: If you have a blog, or website (Flickr album?) you'd like me to list I'd be more than happy to include it. Also if you find you have a reply to this that turns into a short story of it's own I'd be happy to post it as a guest post. Should either be the case e-mail me at MrILoveTheAnts @ yahoo.com
Marris argues that invasives generally cause very little damage and extinctions from invasives are rare. She cites studied that show that even on islands the biodiversity increases after the introduction of invasive plant species.I know I've changed the title of my blog to Biodiverse gardens but I feel like the term gets thrown around as though more of it is a mark of success. Incorporating species that cannot be digested, let alone recognized as food, by indigenous animals is counterproductive. Nonnatives often do nothing but take up space and can ruin the sense of place. Most herbivores are generalists and will give anything a nibble at least once. Marris focuses entirely on these larger animals to support her claims, but she completely ignores insect life though and they are fundamental to the food web. Without them they render non fruiting shade trees useless. There are 285 species of caterpillar that eat our native Maples, the imported Norway Maple only hosts significantly fewer. Among those mentioned are Leaf Rollers, Cankerworm, and Tent Caterpillars, all of whom are generalists eating a wide variety of tree species and have a preference for our native species. We can argue that 286 species of caterpillar are simply speeding up the process of mulch production but at least they double as bird food.
Pound per pound insects have twice as much protein in them as other animal meats. They are the number one food item fed to baby birds, and are a favorite among reptiles, amphibians, fish, and so on. If you don't have an abundance of insects, it can send ripples through the food web.
I like to compare this to eating at the mall food court. Here we have an assortment of food cuisines to pick from but the average person doesn't eat them all. Personally I can't stomach most Mexican food, I'm afraid to try anything Asian, and I've never given Indian food any thought. Insects who typically only have a few weeks to get it right before they die have to lay their eggs in the right spot, or on the right plant, and they have to eat the correct diet for the simple fact that they can't eat anything else. In most cases this is only a hand full of plants, that are almost always in genera that they've closely evolved with.
An example Emma gives to support the benefit of nonnatives is Rodrigues island, found about 350 miles east of Mauritius island off the coast of Madagascar. It is in her book on page 97-98.
View Larger Map
This massive island was supposidly logged, and then supposidly replanted? To be perfectly honest I don't see how either could be done effectively. We're not talking about just an island so much as a small city. She might as well be talking about Hawaii again. Had her book included pictures it might have been apparent to everyone that she was talking about an island inhabited by people.
There are paved roads, houses, air ports, farms, mountains, what look to be beach side resorts. None of this was mentioned in her book. So this is no longer a simple matter of adding and subtracting trees. How many of these people have bird feeders? How many put out bird houses? When she talks about replanting does she mean the bustling agricultural farms scattered all over the island? Are these nonnative trees simply common landscaping plants I can find at my local nursery? She might as well be talking about where I live in New Jersey. We have fragmented forests of native trees, and all the clearings are landscaped with mostly nonnative plants. I even doubt the people who planted them put any thought into their origin.
Wikipedia seems to think the bird issue she mentions was due to over hunting and overgrazing by livestock, not so much logging. Regardless, the issue was habitat lose and we don't regain that with alien species. Emma doesn't seem to mention anything about their conservation efforts to maintain some of their remaining threatened species. Or the captive breeding program for her bat species she mentions. They were eating the fruit to some of the nonnatives such as rose apple, which these birds and bats were likely helping to spread around the island. She just assumes because the bat was eating the nonnative fruits that that's what saved the species. It's a fruit bat, I doubt it cars what it's eating so long as it's fruit.
She ends by saying, "The exotics turned out to help rather than hinder, but prejudice against them was so strong that instead of thanks, they are getting the ax." Correct, god forbid a society try to learn from it's mistakes and give conservation a chance in some attempt at a more predictable wilderness. Had they not over logged the forests to begin with they wouldn't have had any problems. Was that breeding program doing nothing for the bat population? For her to suggest that these nonnative trees were the only factor is misleading.
Further more, I would love to know the exact kind of efforts are being made to control the nonnatives. Because Rose Apple is a food crop I find it hard to believe that they'd totally ban it from the island, unless they've become an island of die hard conservationists, which is a theme she has been quoted as saying. What would make sense to me is that they clear it out from specific areas meant for conservation and still grow it as a viable crop, perhaps even make efforts to hinder it's spread by the animals somehow. You restore habitat by establishing and promoting what has historically grown and worked there to reestablish the norms that sustained it. Fruit and Nectar don't mean nearly as much as the indigenous insect populations and you get that by promoting the native food plants they evolved with.
She eventually follows up by talking about Pyura praeputialis, some sort of sea mussel from what I can gather, and how it's displacing Perumytilus purpuratus. However indigenous starfish and such have already taken a liking to the nonnative and it's looking like things are slowly coming back into balance. This is a 10 times better an example than what's going on in Rodrigues. The trouble I doubt the starfish and such that eat them care which mussel species they feed upon. Everything that supports her claim tend to be generalists who eat a broad range of foods.
In other chapters she talks about how cats and rats and sometimes snakes are awful on islands because they cause mass extinctions of bird populations.
So what is she talking about now? Nonnatives are good and bad sometimes? I really don't get what she's trying to say with this issue other than it's confusing.
You completely missed the point of the first chapter.I don't deny I missed the point of the first chapter. As I wrote in my review I was ready to throw her book in the trash until chapter 2 or 3 came along and things took a dramatic up turn.
She was setting up the invasive argument by highlighting that species distribution is by chance and it's a matter of which species gets there first and these distributions can change radically over geologic timescales this making any baseline attribution completely arbitrary and without intrinsic value.
I loved hearing about different conservation efforts around the world. For me that's the only real highlight and saving grace of this book. She kept concluding though that it's all a waste of time in the grand scheme of things. It really got annoying. If a nose fell off Mt. Rushmore I'd like to think someone would fix it.
Baselines at least give someone an idea of what standards need to be upheld. Every gardener has them even if their goals are short term and change from year to year. National parks happen to be more strict about them.
Since you stopped halfway through the last chapter, you apparently missed the fact that she advocates for protection of biodiversity and native species, argues for increased plantings of native species especially through the elimination of lawns. She just thinks that becoming apoplectic because someone planted Pennisetum setaceum is a waste of valuable resources.Picking the book back up now I found that I'd left off at her suggested goal #6 of 7. So I wasn't that far from the end, it's just that chapter reads like an appendix. Encouraging people to plant native was an afterthought at best. She should have had more to say on it sooner in the meat of the book.
I am for a more generalized view of what's native but the idea of including plants that didn't evolve on the same continent is a silly idea. The only exception I make to this rule is with food plants I know I'm going to control and eat. I feel like if the whole world followed this rule we'd be in a lot better shape.
I don't scoff when people plant nonnative plants, but I feel something should be done about people who actively import them without permits.