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Invasive plants and animals are an expensive problem in the United States.

Federal agencies spent more than $104 million last year to control them. But a study on the garlic mustard plant shows that it might be better to leave some invasives alone.

Garlic mustard is a forest plant with heart-like leaves and clusters of white flowers. It can grow up to about four feet tall and is often the first green plant you'll see in the spring.

Europeans settlers brought it to the United States in the 1800s as an herb for cooking. It was also used to treat ulcers¹ and gangrene.

Paul Vugteveen, a chef in Battle Creek², uses the plant in his cooking. He says it has a garlicky, oniony flavor and is best served raw.

"You can just throw it in at the end of a sauté just to kind of brighten it up," he says.

But this culinary herb has outstayed its welcome. Garlic mustard has spread all over the northeast and Great Lakes region — wiping out native species in its path.

The plant has a secret weapon that makes it so invasive — a chemical called sinigrin. When sinigrin leaches³ into the soil, it kills off a beneficial fungus⁴ that other plants rely on to get nutrients⁵.

But now, scientists have spotted⁶ a weakness. After years of domination, garlic mustard starts giving up the fight.

Richard Lankau, who teaches plant pathology at the University of Wisconsin-Madison, co-authored a recent study on this in the journal Functional⁷ Ecology.

"This weapon if you will, it's not useful when you're competing with other members of your own species," he says.

Lankau's team found that over the span of decades, large populations of garlic mustard stop producing as much sinigrin — which might allow native plants to move back in.

Basically, it becomes less invasive.

If a big, bad invasive species like garlic mustard can stop being as big and bad, should we still try to control it?

Ken⁸ Thompson says maybe not.

Thompson, a retired⁹ ecologist from the University of Sheffield in England, wrote a book called "Where Do Camels Belong? The Story and Science of Invasive Species." He says invasive species have a way of balancing themselves out.

"Over time what happens is the species evolves, the species with which it is competing evolve and this apparent superiority slowly begins to decline," says Thompson.

He says the invasive species we should be worried about the most is us. People have destroyed native habitats and brought in invasive species without thinking of the consequences.

"Very often the root cause of the invasion are the changes to the environment that we have made," he says. "I mean, how likely would it be—after all the changes we've made to the world—that the native species that used to live in all those very changed habitats are now the best species adapted to live there?" ?

Thompson says often methods used to control invasive species, like spraying herbicides, do more damage than the species itself.

Thompson says in a century, garlic mustard probably won't be any more of a problem in the U.S. than it is in the U.K. But it's what might happen in that hundred years that worries the authors of the study.

Lankau says when invasive species take over, there's less diversity of the plants and animals that make up a healthy ecosystem¹⁰.

"One sort of take-home message is that we shouldn't necessarily apply the same strategies all over the country," he says. "There are places where the invasion is sort of hot and heavy where it's probably worth investing a lot of resources in and there are places where it's cooled off a little bit and maybe our resources are better used in other ways."

Ryan Koziatek is a local invasive species manager and the stewardship¹¹ field director for the Kalamazoo Nature Center. He says last year volunteers pulled 10,000 pounds of garlic mustard at the nature center alone—that's the weight of two rhinos¹².

Koziatek isn't ready to change his strategy for dealing¹³ with garlic mustard just yet—but it's worth talking about.

"So at this point it's kind of a nice to know and something to consider moving forward."

Great Lakes Today is a collaboration¹⁴ of WBFO Buffalo¹⁵, ideastream Cleveland, and WXXI Rochester.

1 ulcers   

n.溃疡( ulcer的名词复数 )；腐烂物；道德败坏；腐败

参考例句：

• Detachment of the dead cells produces erosions and ulcers. 死亡细胞的脱落，产生糜烂和溃疡。 来自辞典例句
• 75% of postbulbar ulcers occur proximal to the duodenal papilla. 75％的球后溃疡发生在十二指肠乳头近侧。 来自辞典例句

2 creek   

n.小溪，小河，小湾

参考例句：

• He sprang through the creek.他跳过小河。
• People sunbathe in the nude on the rocks above the creek.人们在露出小溪的岩石上裸体晒日光浴。

3 leaches   

n.（将化学品、矿物质等）过滤( leach的名词复数 )；（液体）过滤，滤去

参考例句：

• People consume it when it leaches from plastic into baby formula, water or food in container. 当它被从塑料中经沥滤而入婴儿配方奶粉、水或罐装食品当中的时候，人们将其摄入。 来自互联网
• After this article uses is also the microwave pretreatment, leaches the method with the solution. 本文采用的也是微波预处理后用溶液浸取的方法。 来自互联网

4 fungus   

n.真菌，真菌类植物

参考例句：

• Mushrooms are a type of fungus.蘑菇是一种真菌。
• This fungus can just be detected by the unaided eye.这种真菌只用肉眼就能检查出。

5 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

6 spotted   

adj.有斑点的，斑纹的，弄污了的

参考例句：

• The milkman selected the spotted cows,from among a herd of two hundred.牛奶商从一群200头牛中选出有斑点的牛。
• Sam's shop stocks short spotted socks.山姆的商店屯积了有斑点的短袜。

7 functional   

adj.为实用而设计的，具备功能的，起作用的

参考例句：

• The telephone was out of order,but is functional now.电话刚才坏了，但现在可以用了。
• The furniture is not fancy,just functional.这些家具不是摆着好看的，只是为了实用。

8 ken   

n.视野，知识领域

参考例句：

• Such things are beyond my ken.我可不懂这些事。
• Abstract words are beyond the ken of children.抽象的言辞超出小孩所理解的范围.

9 retired   

adj.隐退的，退休的，退役的

参考例句：

• The old man retired to the country for rest.这位老人下乡休息去了。
• Many retired people take up gardening as a hobby.许多退休的人都以从事园艺为嗜好。

10 ecosystem   

n.生态系统

参考例句：

• This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
• We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。

11 stewardship   

n. n. 管理工作；管事人的职位及职责

参考例句：

• The organization certainly prospered under his stewardship. 不可否认，这个组织在他的管理下兴旺了起来。
• Last, but certainly not least, are the issues of stewardship and ethics. 最后，但当然不是微不足道的，是工作和道德规范的问题。

12 rhinos   

n.犀牛（rhino的复数形式）

参考例句：

• There are many reports of people taming and even training Indian rhinos. 有许多关于人们驯养甚至训练印度犀牛的记载。 来自辞典例句
• The rhinos had fed during the night in the rice fields of these villagers. 犀牛夜里在这些村民的庄稼地里也已吃饱了。 来自辞典例句

13 dealing   

n.经商方法，待人态度

参考例句：

• This store has an excellent reputation for fair dealing.该商店因买卖公道而享有极高的声誉。
• His fair dealing earned our confidence.他的诚实的行为获得我们的信任。

14 collaboration   

n.合作，协作；勾结

参考例句：

• The two companies are working in close collaboration each other.这两家公司密切合作。
• He was shot for collaboration with the enemy.他因通敌而被枪毙了。

15 buffalo   

n.(北美)野牛；(亚洲)水牛

参考例句：

• Asian buffalo isn't as wild as that of America's. 亚洲水牛比美洲水牛温顺些。
• The boots are made of buffalo hide. 这双靴子是由水牛皮制成的。