One of the reasons for a traffic drop can also be due to your site losing links. You may be seeing a direct loss of that referral traffic, but there could also be indirect effects. When your site loses inbound links, it tells Google that your site isn't as authoritative anymore, which leads to lower search rankings that in turn lead to traffic drops (because fewer people are finding your site if it's not ranked as highly and more).
An organic marketing strategy generates traffic to your business naturally over time, rather than using paid advertising or sponsored posts. Anything you don’t spend money on directly – blog posts, case studies, guest posts, unpaid tweets and Facebook updates – falls under the umbrella of organic marketing. That email blast you just sent out? Yup, that’s organic. So is that user-generated content campaign you just launched.
At our agency, we work with sites of varying sizes, from very large to quite small, and recently, we have noticed a trend at the enterprise level. These sites aren’t relying as much on Google for traffic any more. Not only are they not relying on Google traffic, but also, the sites are getting less than 10 percent (or slightly more) of their organic traffic from the search giant.