Katie H. Morrow

The niche has been central to ecology for most of the discipline’s history, yet there have been few attempts by philosophers to work out the ontology of the niche. A challenge is that there is a plurality of seemingly inconsistent definitions of the niche in ecology. This paper characterizes the population-level ecological niche by distinguishing among niche concepts, niche models, and the niche as a phenomenon. I argue that 'niche concepts' should be interpreted as theoretical frameworks or modelling strategies. I also argue that there is a unified niche phenomenon underlying the seemingly heterogeneous models and definitions. The plurality of niche concepts in ecology should be seen as an expected consequence of the nature of modelling complex systems.

Ecological neutral theory has been controversial as an alternative to niche theory for explaining community structure. Neutral theory, which explains community structure in terms of ecological drift, is frequently charged with being unrealistic, but commentators have usually not provided an account of theory or model realism. In this paper, I propose a framework for comparing the “realism” or accuracy of alternative theories within a domain with respect to the extent to which the theories abstract and idealize. Using this framework I argue, contrary to most previous commentators, that neutral and niche theories are similarly realistic. Realism cannot provide a basis for accepting or rejecting either type of theory; instead, community ecologists should continue working with a plurality of models. While theoretical unification may become possible, we should treat a plurality of complementary, partial models as the expected situation within community ecology.

This paper addresses the stalemate on the question whether biodiversity has intrinsic value. I distinguish between a “weak” conception and two “strong” conceptions of intrinsic value in the environmental ethics literature. The strong conceptions of intrinsic value are connected, respectively, to moral standing and to a strongly objectivist account of value. Neither of these forms of value likely applies to biodiversity. However, the weak conception of intrinsic value is neutral about both moral standing and the nature of value and plausibly applies to biodiversity. In addition, weak intrinsic value avoids common objections to the claim that biodiversity is intrinsically valuable. I develop a cumulative argument showing that environmentalists should presume that biodiversity has intrinsic value in the weak sense.

I develop an account of ecological role functions—the functions of species within ecosystems—which is informed by alternative regime phenomena in ecology. My account is a causal-role theory which includes a counterfactual sensitivity condition. The account tracks and explains a distinction ecologists make between functions and various activities which are not functions. My counterfactual sensitivity condition resolves the liberality problem often attributed to causal-role theories of function, while also illuminating the explanatory centrality of role functions within ecology.

The ecosystem services argument is a highly publicised instrumental argument for protecting biodiversity. I develop a new objection to this argument based on the lack of a causal connection from global species losses to local ecosystem changes. I survey some alternative formulations of services arguments, including ones incorporating option value or a precautionary principle, and show that they do not fare much better than the standard version. I conclude that environmental thinkers should rely less on ecosystem services as a means to defend biodiversity, and that attention should be focused on additional types of value which might be attributed to global biodiversity.