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Resistance is a community's ability to withstand disturbance without changing composition. Resilience is its ability to recover after disturbance. Diversity often increases both properties, though the relationship is complex. Stability trades off with productivity—highly productive systems are often less resistant to disturbance.
From your study of community ecology and ecological succession, you know that communities are not static — they change in response to disturbance and over time. But some communities absorb shocks while others collapse. The concepts of resistance and resilience provide a framework for understanding these differences. Resistance is the ability to remain essentially unchanged during a disturbance — a resistant forest barely shifts in species composition during a drought. Resilience is the ability to bounce back afterward — a resilient grassland recovers its original species mix within a few years of a fire. A community can be high in one property and low in the other: old-growth forests are often highly resistant (stable for centuries) but poorly resilient (if cleared, they take hundreds of years to recover), while grasslands may be easily disturbed but snap back rapidly.
The relationship between diversity and stability has been debated since the 1950s, but a large body of experimental evidence — particularly David Tilman's long-term grassland experiments at Cedar Creek — shows that more diverse communities tend to be both more resistant and more resilient. The mechanism is often called the insurance hypothesis: in a species-rich community, if one species declines during a drought, other species with different drought tolerances can compensate, maintaining overall community function. In a species-poor community, losing one of only a few species can cause the whole system to crash. Functional redundancy — multiple species performing similar ecological roles — provides a buffer against environmental variability.
However, the diversity-stability relationship is not a simple rule. Highly productive systems can be surprisingly fragile. A monoculture cornfield is enormously productive but collapses entirely under the wrong pest or weather event. Conversely, species-poor but highly adapted communities — like desert scrublands — can be remarkably resistant to the specific stresses they evolved under, yet devastatingly slow to recover from novel disturbances like grazing or development. The type of disturbance matters too: a community resistant to fire may not be resistant to flooding.
These concepts have direct conservation and management implications. When ecologists assess a threatened ecosystem, they ask not just "how many species are here?" but "how will this community respond to climate change, invasive species, or land-use change?" A community with high resistance buys time — it persists under pressure, giving managers a window to intervene. A community with high resilience is more forgiving — it can recover from management mistakes. Understanding which property a given ecosystem possesses, and why, guides decisions about where to invest limited conservation resources and whether to prioritize protection (leveraging resistance) or restoration (leveraging resilience).