drier means lower in amount of water & a dry environment is low in availability of water ->  as dryness increases in an environment , the available water in that environment will decrease  as dryness increases in an environment , the available water in that environment will decrease & living things require water for survival ->  as dryness in an environment increases, the ability of living things to survive in that environment decreases due to a lack of available water  as dryness in an environment increases, the ability of living things to survive in that environment decreases due to a lack of available water & storing water increases the water available to organisms in a dry environment ->  as a living thing's ability to store water increases, that living thing's ability to survive in a dry environment increases  as a living thing's ability to store water increases, that living thing's ability to survive in a dry environment increases & if something increases something else then that something has a positive impact on that something else ->  ability to store water has a positive impact on an living thing's survival in a dry environment  ability to store water has a positive impact on an living thing's survival in a dry environment & an adaptation has a positive impact on a living thing 's survival -> ability to store water is a kind of adaptation to a dry environment