Best Ways for Species to Spread Across Two Habitats for Stability

Greg Howard
23rd February, 2024

Image Source: Natural Science News, 2024

Understanding the delicate dance of species survival in fragmented habitats is a bit like watching a complex ballet. Each movement, or in this case, each individual's decision to stay or migrate, can influence the entire performance. Scientists at the Centre de Recerca Matemàtica have taken a closer look at this intricate interplay with a new study^[1] that sheds light on how dispersal—the movement of individuals from one place to another—affects the overall health and longevity of species populations living in separate but connected environments, known as metapopulations. Imagine two islands of habitat, each with its own population of a species. These islands are like two patches in a quilt, and the species can move between them along threads of dispersal. The researchers used a mathematical model to simulate the life of these populations, considering how individuals might move between the patches and how this movement affects the species' survival. The study builds upon previous research that has shown sudden changes in populations are common, especially when the environment is disturbed^[2]. These changes can be dramatic, like a cascade of dominos falling, as individuals decide to leave an area, influencing others to do the same in a process known as social copying. This can lead to a tipping point where so many leave that the population collapses. Other studies have looked at how the movement of species between different areas can either help or harm their overall numbers^[3]. Sometimes, moving too much can actually decrease the number of individuals in both the area they left and the area they move to, especially if the two populations compete for resources. The new research delves deeper into this phenomenon, examining how different levels of dispersal can either protect or endanger these populations. At low levels of dispersal, populations are at risk of dying out due to random events, as they are not well-connected enough to support each other. However, as dispersal increases, the populations become more robust, able to withstand unexpected changes. Interestingly, the study also confirms that a little inequality between patches can be a good thing. If one patch is thriving while the other is not, allowing individuals to move from the less successful to the more successful patch can actually boost the total number of individuals across both patches. This finding is a significant addition to our understanding of metapopulation dynamics, as it provides a formula for the optimal amount of dispersal needed to maximize the total population. This insight is particularly useful for conservation efforts. For example, a previous study^[4] suggested that creating new paths between patches should be done with care, as not all connections will have a positive effect. The new study offers a more nuanced understanding of when and how these connections can be beneficial. Moreover, the research challenges the traditional logistic model, which has been the standard for understanding population dynamics in fragmented habitats^[5]. The logistic model suggests that populations grow until they reach a certain size that the environment can support, but this new study shows that the reality is more complex when considering multiple patches and the movement between them. In summary, the study from the Centre de Recerca Matemàtica provides a clearer picture of how dispersal affects the survival of species in fragmented habitats. It highlights the importance of considering the amount and direction of movement between patches to ensure the long-term health of populations. This research not only advances our theoretical understanding of population dynamics but also offers practical guidance for managing and conserving wildlife in our increasingly fragmented world.

Environment Ecology Animal Science