A recent assessment of the status of global amphibian populations identified habitat loss as the single greatest identifiable factor contributing to amphibian declines. Habitat loss primarily results from the residential, agricultural, arboricultural, or recreational development of an area. Anthropogenic conversion of land has caused significant reductions in the wetland, forest, and grassland habitat that amphibians require for their survival. Outright habitat loss probably has the greatest effect on amphibians, but habitat degradation, or the general decline in the health of a habitat, often results from environmental contamination, the introduction of exotic invasive species, or a reduction in required resources within a habitat, and similarly affects amphibians. Likewise, habitat fragmentation (the disruption or fragmentation of habitat into discontinuous or isolated remnants of viable habitat) emerges from isolated patches of habitat loss and can often have delayed effects on animal populations.