Dr. Johnson thinks that everyone should take responsibility for preserving the toad species. Not mowing certain areas of our wild grass can be kept for toads. This practice may help to protect the species. According to Dr. Johnson, dangerous chemicals found in pesticides and fertilizers are the toads disappearing. The chemicals affect the food chain and kill the insects that toads eat. Dr. Johnson believes that the toads can be saved if we keep a space in our yards and stop using chemical fertilizers.

Which of the following details in the above text explains that toads are starting to vanish?