AP Syllabus focus:
‘Human activities accelerate local and global ecosystem changes, including biomagnification and eutrophication that can cause extinctions.’
Human activities rapidly reshape ecosystems by altering nutrient cycles, introducing toxins, and changing habitat structure. These disruptions can cascade through food webs, reduce biodiversity, and, in severe cases, drive population declines and extinctions.
Human-driven ecosystem change
What “accelerate change” means ecologically
Human actions often increase the rate, magnitude, and geographic reach of environmental change beyond what many populations can adapt to on ecological timescales. Key pathways include:
Practice Questions
FAQ
Some evaporate and condense repeatedly (“global distillation”), moving via air currents.
Others travel in rivers and ocean currents, then enter food webs through plankton and sediments.
Warm water holds less dissolved oxygen.
Higher temperatures can also speed microbial respiration, increasing oxygen demand during decomposition.
Scientists sample multiple trophic levels and measure contaminant concentration in tissues.
Stable isotopes (e.g., $^{15}!N$) can help estimate trophic position to relate concentration to trophic level.
Riparian buffer strips and wetlands
Cover crops and reduced tillage
Precision fertiliser timing/dosing
Upgraded wastewater treatment to remove nutrients
Nutrients stored in sediments can be released later (internal loading).
This legacy effect can sustain blooms until sediments are stabilised or nutrient stores are depleted.
