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Although the evidence is limited , owing to the small numbers of subjects examined , the data across studies suggest that the effects of hearing loss on speech production are most pronounced if the hearing loss occurs in the teens and early twenties than if it occurs in later adulthood . There is certainly more awareness of conservation , the effects of pesticides and other toxins on wildlife and the environment , the consequences of habitat loss and degradation , and the importance of biodiversity . Without understanding the dangers of language loss ( Wong-Fillmore , 2000 ) and how long it takes for language minority students to reach monolingual English norms ( Thomas & Collier , 1997 ) , even well-meaning teachers will see linguistic diversity not as a resource , but as something to be remediated ( Austin , 2003 ) . The rates of tooth loss in men were significantly reduced after they quit smoking cigarettes but remained higher than those in non-smokers . In all cases , attempts at sustainable management have been hampered severely by a lack of economic considerations - either of the value of wetland goods and services , of the causes of wetland loss , or of the potential for economic tools to support sustainable river basin management .