PARENT SESSION
Oral Session # 44: Resource Management I: Theory; Aquatic Systems.
Presiding: C Swan
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 106.

A comparison of the effects of ecosystem management and unintended anthropogenic impacts on community richness, diversity and abundance.

Eatough Jones, Michele^*,1, Paine, Timothy¹, Hare, J. Daniel¹, ¹ University of California, Riverside, Riverside, CA

ABSTRACT- Human activities are widely reported to impact ecosystems on both local and global scales. These alterations can negatively affect ecosystem goods and services that we rely on. Species richness is frequently used as an indicator of ecosystem health. Loss of species is assumed to be one of the driving mechanisms for changes in ecosystem function. We compared effects on communities for two categories; intended alterations through management activities and human activities with unintended ecosystem impacts. Management activities included logging, fire, pesticides and species introductions for biological control. Unintended impacts included pollution, habitat fragmentation and invasive species. We surveyed ca. 120 studies examining community richness, diversity and abundance responses from a variety of trophic levels and taxonomic groups. Study outcomes were scored as increased, decreased or no change for each community index. We assumed the direction of community change would be random and ² tests were performed to see if all outcomes were equally likely. Abundance and diversity had non-random outcomes for both types of alterations. Effects on species richness were non-random for unintended impacts but not for managed systems. Community abundance was affected similarly by both impacts (decreased in 60% of studies), but species richness and diversity more often decreased due to unintended impacts (60%, 70%) than for management activities (40%). Vertebrate communities showed the largest difference in response to management activities and unintended impacts. They were unlikely to be altered in response to management activities, but showed decreased richness with unintended impacts. Plant, arthropod and nematode communities were more sensitive to unintended impacts than management activities. Across pooled trophic levels, we found differences in the way communities respond to managed and unintended impacts. Community abundance decreased in response to both types of alterations, but richness and diversity were more often maintained under management activities. Within taxonomic groups, unintended impacts most often resulted in negative community responses, but management activities had variable effects.

Key words: species richness, community abundance, species diversity, anthropogenic impact