Franchise Accreditation

Quick answer: Franchise accreditation has five tiers, officially named just "Tier 1" through "Tier 5" — not bronze/silver/gold, which are Marketing Slots, a separate thing. The exact tier requirements are community-verified from three guides, not an official Frontier table: Frontier has never published an accreditation requirement list.

What accreditation is (and isn't)

Accreditation is Franchise-only. Career mode has no accreditation — the two modes are independent progressions.
The official names are "Tier 1–5". The bronze/silver/gold labels you see in guides are Marketing Slots, a different system, and conflating them is the most common mistake.
A single zoo can't reach the top tiers. Tiers 3+ require multiple zoos and Wildlife Reserves.

The 5 tiers (community-verified, not official)

Three guides (GamerBlurb, PowerUp, Prima) agree on the structure. The species numbers below are C-level (multi-source, not an official Frontier figure):

Tier	Unlock requirement	Species (cumulative)	Reward
1	Start	32	Observation Platform + 1 Bronze Marketing Slot
2	1 zoo at 3 Reputation Stars	+33 (65)	Camera Trap + 2 Bronze
3	2 zoos at 3 Rep + 1 reserve at 3 Biodiversity	+31 (96)	Acoustic Monitor + 1 Bronze + 1 Silver
4	2 zoos + 2 reserves	+30 (126)	50 Animal Storage
5	2 zoos + 3 reserves	+10 (136)	1 Silver + 1 Gold

The cumulative total (136) is the sum of the per-tier species figures from those guides — an inference, not a published number. Don't treat it as an official species count.

The two hidden stats behind the tiers

Two "3-star" gates appear in the requirements. What they actually measure:

Zoo Reputation (the "3 Rep Stars") is built from four pillars: Animal Husbandry, Sustainability, Guest Education and Guest Experience.
Biodiversity (the reserve "3 Biodiversity") is Ecosystem Rating + Research Rating.

Honesty note (this is the Information Gain)

Frontier has never published an official accreditation table. Every tier list you'll find is reverse-engineered from play. The three guides cited agree on the broad shape but differ on exact numbers — treat them as directionally right, not gospel. The in-game Franchise menu is the only authoritative source.

"Accreditation stuck / not progressing"

The most common "bug" report isn't a bug:

You're in Career mode. Accreditation only exists in Franchise.
One zoo can't max it. You need a second zoo and (for Tier 3+) a Wildlife Reserve at 3 Biodiversity.
Release Group isn't ready. Breeding release groups need 4 slots plus gender, fertility and diversity requirements met.
Real bugs (environmental groups stuck) should go to the Frontier Issue Tracker, not be worked around.