geneva west african migrants try reach europe die far great number sahara mediterranean efforts dissuade may cause new rout open unite nations migration agency say thursday far year 2,569 migrant deaths record central mediterranean 107,000 migrants mainly west africans reach italy one thing still estimate number deaths desert richard danziger u.n. international organization migration director west central africa tell news conference geneva assume think say least double die mediterranean really evidence assumption know niger main transit route people smugglers increasingly scar authorities might make prone abandon migrants desert say many migrants tell deaths desert say smugglers believe drive fast minefields would safe say iom niger mission chief giuseppe loprete migrant number head niger fall dramatically strong action government close migrant ghettoes arrest people smugglers say iom also try spread word want get catch libya danziger say happen libya far scary people die horror stories returnees come back many smugglers see criminals often former desert guide try make money many give organize criminals contact libya continue loprete say right look alternative rout think least equally dangerous say plug one hole hole go open danziger say niger two rout libya one close chad use smuggle migrants one close algerian border far dangerous use extremist group drug gun-running alternative northern mali region beset conflict rival group seem dramatic rise danziger say route consider safe along western coast africa via senegal mauritania morocco strait gibraltar migrant flow increase say migrant deaths sahara likely twice mediterranean toll u.n