No, that's not true. There are precisely zero species we rely upon in that way. For instance, we have very heavy dependence on wind-pollenated crops or crops that don't need pollenation at all (e.g. potatoes, cassava). We can take everything utterly essential and transport it above 30 degrees latitude, if absolutely necessary.

Of course the consequences of 10C warming--which isn't predicted, but which would necessitate that--would be catastrophic. Without exaggeration, it would be the worst calamity to ever befall Homo sapiens.

But we won't starve. Plankton are moved around by ocean currents. High-altitude species survive with lower oxygen. So on and so forth. You are massively underestimating the resilience of life as a whole, and humans specifically, when you're talking about extinction.

I'm not okay with people suffering, with us losing our ability to maintain an advanced technological society that affords us pleasant lives, and so on. Far from it.

However, exaggeration does not help. Accurately appraising the nature and likelihood of risks is tremendously empowering because you realize where to put what effort you have (whether it be self-preservation despite the changes, or to prevent the changes).

Exaggeration makes it worse because people waste effort trying to mitigate fantastical scenarios that won't happen, sacrificing effort that they could have put into mitigation of likely scenarios.