[In the spirit of Earth Day this week, I'm going to brainstorm some ideas for games with an ecological or natural theme. Imagine these games printed on 100% recycled chipboard. Also see my post on sustainable game components.]
A while back, I had this loose image of a Pre-Columbian village on the Pacific coast of South America. The village doctors would travel from the coast, past the Andes, into the Amazon basin looking for strange and mysterious ingredients for potions. That idea stuck in my head for a while, but now I'm thinking about a slightly different theme.
The game is set in more modern times. The Amazon rain forest has potentially life-saving medicinal plant life. Each player is a doctor, traipsing through the Amazon and discovering patches of plant life. You are trying to collect just the right kind of plants, but still leave enough behind to regrow over time. With the right plants, you can cure certain patients and they'll return the favor in various ways.
The game is comprised of a Plant deck (various fictional plants and flowers), a Medicine deck (split into six different types of medicine), a Patient deck (ailments that require certain combinations of medicine to cure), and standard dice.
Each plant card is a slightly modified version of the Bomb's Away! board. Here are three examples.
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A tableau of plant cards are laid out in the middle of the table, much like those seen above. The numbers 1-6 represent different types of medicine with varying rarity. 1s are most common and 6s are least common. In the final game, these would have cute scientific names like "Oneum" "Twosia" "Threed" "Foural" "Fiven" and "Sixic."
On your turn, you roll one die to "harvest" medicine from one of the plants. You must place that die on the lowest unoccupied space a row matching the die's result. So, a  die must go in the lowest unoccupied space in any available  row on any card in the tableau. If any plant gets six or more dice on it, the plant is discarded and a new plant takes its place in the tableau.
Then, you may gather medicine from that chosen plant. Each type of medicine card is arranged in its own deck. So, all the Oneum medicine cards are in their own clearly visible stack, as are the Twosias, Threeds, Fourals, Fivens, and Sixics. You draw a Oneum if you got a 1 result, Twosia if you got a 2 result, and so on. The number of medicine cards you may draw depends on how high up the track you placed your die. If in the second space, you may draw two medicine cards. If in the third space, you may draw three medicine cards, and so on.
So, what do you do with medicine? You have a hand of Patient cards. Each patient describes the cure that they need and what they'll offer in return for the rest of the game.
CURE: Oneum x3
REWARD: Grad Student: You may re-roll one die when harvesting plants.
CURE: Oneum + Twosia + Threed + Foural
REWARD: Private Garden: Draw a plant. Only you may harvest from it.
CURE: Foural + Fiven + Sixic
REWARD: Tribal Guide: Roll an additional die when harvesting. Choose a result.
When you spend medicine to cure a patient, that patient goes in front of you so everyone can see the reward. The medicine cards go into a discard pile. At the end of each round, discard one patient from your hand and draw a new one. At the end of each round, one each medicine is taken from the discard deck and returned to its stack. (Representing the regrowth of the local ecosystem.)
However, if a stack of medicine ever runs out, it cannot be replenished. Once it's gone, it's gone. So, there is a tension in trying to collect the most valuable medicines but also doing so in a manner that won't completely deplete the supply.
After X number of rounds, players score points from their patients. You also score points based on the kind of medicine you have in your possession. The medicine's point value is determined by how much of that medicine is still in its respective stack. If 0 cards remain, it is worth 0. If one remains, it's worth one point. Up to a maximum of three points per medicine card. This creates another incentive not to deplete a medicine stack too much.
So, that's the rough idea. It would need a solid balance between the rarities of each medicine, the rewards from each patient, their point values, and making sure the whole game just moves at a quick pace. It would also need some testing to determine the appropriate length of game.
UPDATE: In hindsight, it may be more appropriate to call the Plant cards Region cards instead. This unifies the terms "plant" and "medicine" into a single game concept. Then, the region cards simply represent patches of rainforest where the plants are available. Yeah, that makes a lot more sense.