A habitats unit almost always comes out as a list of places. Desert, pond, reef, rainforest, tick them off, and the children finish able to name five biomes and explain nothing. These eight books are picked so that they each teach a mechanism instead: how a fallen log becomes soil, how a pond is stacked in layers, how a reef is built out of its own dead, what happens to everything else when the wolves come off an island. Hand each child the one that fits their reading and let the class come back together to talk. One of them is not about a habitat at all. One Small Square: Pond is the method for studying one, and if you want the children doing science rather than reading about it, that is the book to build on. Read the heads-up on Wolf Island before you read it to a room.
The eight books answer one question — how does a habitat actually work — and any one of them satisfies the whole idea on its own. Pick by the child, not by the number. What makes it a unit rather than a pile is that the books each teach a different mechanism, and between them they cover most of what ecology is. A Log's Life is decomposition and what comes after it: one oak on the forest floor for two hundred years, until it is soil and the next oak grows out of it. Over and Under the Pond is the layered habitat, the idea that a place has a top and a bottom with different lives at each, which is the most portable thing on this shelf. Coral Reefs is construction and symbiosis: coral is an animal, it builds rock out of the skeletons of the dead ones below it, and the living part runs on algae lodged inside it. About Habitats: Deserts is adaptation, said as plainly as it can be said. A Place for Butterflies is the mechanism of loss, named eleven times with a cause and a place attached each time. And Wolf Island is the food web, which it teaches by breaking one: take the wolves off, watch the deer multiply and eat the island bare, watch everything else starve. That is the hardest idea in the unit and it is the only book here that goes near it. Two things to know before you plan. One Small Square: Pond is the odd one in the best way — it is not about a habitat, it is the method for studying one. Mark out a square about a yard across, look at it over and over, write down what is in it. That is a real protocol and a class can run it on Tuesday, so if you want the children doing science rather than reading about it, build the unit on that book and arrange the other seven around it. And The Great Kapok Tree is the odd one out in the other direction. It is a fable — a man dozes off at the roots and ten talking animals take turns persuading him — and persuading is a different act from describing. Its rain-forest facts are from 1990 and have aged badly. It is on the shelf because it is lovely and it is about a rainforest, and it is worth telling a class outright that this one is arguing while Sill is describing. That contrast is the best thing this shelf can teach about how books work.