Valmiki Ramayana Ayodhya Kanda Sarga 28 Shloka 10

मार्गाः the paths, लताकण्टकसङ्कीर्णाः full of thorny creepers, कृकवाकूपनादिताः echoing with the noise of wild fowls, निरपाः with no water, सुदुर्गाः च are extremely difficult to traverse, अतः therefore, वनम् forest, दुःखम् is a difficult place.

. The paths full of thorny creepers, echoing with the noise of wild fowls, and with no water (to drink) are difficult to tread. So forest is a source of suffering.