Dr. Johnson thinks that everyone should take responsibility for preserving the toad species. By not mowing certain areas of our lawns, special areas of wild grass can be kept for toads. This practice may help to preserve the species. According to Dr. Johnson, dangerous chemicals found in pesticides and fertilizers are the reason that the toads are 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.

What details in the above text tell us that toads are starting to vanish?