1 . Farms are battlefields, forcing growers to fight against greedy pests and aggressive weeds in never- ending, costly campaigns that often involve chemical weapons. Those weapons also harm innocent bystanders such as bees and fish. Now, a study chart's impressive shifts in recent decades as U. S. farmers have changed their types of pesticides. Birds and mammals have been affected less, whereas pollinators are suffering. The toxic (有毒的) impact on land plants has also increased sharply, likely because farmers are using increasing kinds of chemicals to fight weeds that have become resistant to common herbicides( 除草剂).

As a research shows, in recent decades, the amount of pesticides used in the United States has gone down by about 40% . But active ingredients have become more powerful. For example, fast-acting pesticides are very toxic. Some require as lite as 6 grams per hectare, compared with several kilograms of the older pesticides. Ralf Schulz, an ecotoxicologist, wondered whether overall toxicity in the ecosystem had changed. A few studies had looked at certain compounds and organisms, but nothing had been done on a national scale.

Schulz and colleagues started with U. S. Geological Survey data on self- reported pesticide use by U. s. farmers from 1992 to 2016. They also gathered toxicity data from the U. S. Environmental Protection Agency on those same compounds-381 in all, The good news is that total toxicity decreased more than 95%, for birds and mammals from 1992 to 2016, largely because of the phaseout (逐步停止) of older pesticides. Toxicity for fish declined by less- about one-third.

Schulz hopes more researches will help policymakers and others think more about the complexity of pest and weed control, and wild species, in order to reduce unintentional harm. The rising toxicity in plants could lead to less diverse habitat and food resources that eventually spread to animal populations, potentially causing losses. “The patterns in the U. S. pesticide use and toxicity data should be a warning for the rest of the world, much of which seems to be leaning more heavily on pesticide use rather than ecological interactions for pest control,” Schulz said.

1. What do U. S. farmers usually do to fight against pests and weeds?

A．They change land plants.	B．They use chemical weapons.
C．They harm innocent bystanders.	D．They increase kinds of pollinators.

2. How did Schulz and his coworkers carry out their study?

A．By giving examples.	B．By analyzing data,
C．By doing experiments.	D．By interviewing farmers.

3. Which of the following best describes Schulz's attitude to pesticide use?

A．Subjective.	B．Doubtful.
C．Negative.	D．Favorable.

4. What will happen if toxicity in plants continues to increase?

A．Unintentional harm will be reduced.	B．People will have less food resources.
C．Ecological interactions will increase.	D．The number of animals will decrease.