Not sure if the cron environment or the crontab itself will support the use of scp in that shell the way you want to use it. I'd suggest pulling the scp command out into some script file and then running the script, after you explicitly set any required or assumed environment variables. Something like:
* * * * * /path/to/script.sh
where /path/to/script.sh is your new script and inside it, you have:
#!/bin/bash
export ENVIRONMENT_VAR=foo
#whatever else you need
scp -r root@cloudservername:/backups/databasename.sql.gz > /tmp/output.log
Unsolved 
