Alright, only two of these actually call themselves manifestos. But here are some essays that strongly influenced solarpunk, or that we feel are important to solarpunk as we understand it.
In reverse chronological order:
This essay laid out the ideological hooks that drew a lot of people to solarpunk out of frustration with the dystopia and apocalypse endemic to contemporary science fiction. It was the first document relating to solarpunk that Watson read, and the one they most frequently link people to when pitching the genre and movement.
This post really kicked off contemporary solarpunk, giving the movement its earliest roots in a community and an aesthetic language. The community has expanded on and diverged from the content of that post in all kinds of ways since then -- it's a great post and great inspiration, but we don't want our authors to feel bound to Olivia's original thoughts.
The similarity in this essay's title to Adam Flynn's should tip you off to a strong influence here, but we feel it's important to emphasize that postcyberpunk lacks several elements we feel are essential to solarpunk. It doesn't intrinsically recognize the toxicity of existing power structures; it's explicitly middle-class; it contains no mention of diversity or social justice; and most importantly, it fails (reasonably given when it was written) to engage with the number one catastrophe that solarpunk needs to address: climate change.
In Watson's younger, slightly more obnoxious years, they were enamored with this piece. Looking back on it now, the writing makes them cringe and they feel less universally comfortable affirming everything in it. Still, many of the points directly inform or reflect the values held by Solarpunk Press: for example, Item 15, "If you want better media, go make it." Or the final note, "Capitalism for good or ill is the river in which we sink or swim[.]" But like "Notes Toward a Postcyberpunk Manifesto," it fails to engage with climate change.
This list felt like it would be incomplete without this one. It addresses early and often the major problems with industrial capitalism that we're still dealing with. That said, solarpunk as we understand it is not communist or Marxist; for one thing, Marx and Engels were not nearly as aggressively anti-modernist as we are. Marx laid the undeniable foundation for the politics we now affirm, but it's a relationship like Newton has to contemporary physics, or Darwin to biology: useful but not remotely approaching complete.