  Ecosystems, which are intricate amalgams of biological communities and their
surrounding environments, continually evolve under the influence of their
myriad interactions. The world is currently facing intensifying environmental
fluctuations. Understanding general trends in ecosystem transformations in
response to environmental fluctuations and elucidating the underlying
mechanisms are thus critical challenges. In this study, we used a model
ecosystem approach to investigate ecosystem alterations caused by escalating
environmental fluctuations. We analyzed two distinct models: a stochastic
ecosystem model with a spatial structure, and a differential equation model for
resource competition. We found that environmental fluctuations tend to shift
multi-species coexistence toward the dominance of specific species. We also
categorized biological species as specialists or generalists and discovered
that which of these groups becomes the dominant species depends on the
intensity and frequency of environmental fluctuations. We also determined that
a qualitative change in the diversity-stability relationship depends on the
period of environmental fluctuations. These results underscore the need to
explicitly consider the type of perturbation when discussing ecological
transitions and the stability of ecosystems. Our findings advance understanding
of the mechanisms underlying how environmental changes reshape ecosystems and
offer insights into ecosystem sustainability in the face of future
environmental perturbations.
