Overall Rating: Orange. This means that
guardian of nature is an OK spell.
Overall Notes: Can be beneficial for STR builds, like a melee ranger or Circle of the Moon druid, because it essentially acts as a hunter's mark with the added upside of advantage on all attacks, extra movement, and darkvision. For ranged builds, getting advantage to your attacks will enable more potential for crits and the advantage on CON saving throws can help with concentration. The difficult terrain aura will help with enemies who are looking to approach. Either way you swing it, this is a decent value for a 4th-level spell slot and concentration but probably has more value for STR builds.