Research in Agricultural and Urban Areas in Galapagos: A Biological Perspective

Abstract

Agricultural and urban areas in the Galapagos Islands represent only about 3 % of the terrestrial environments, but their relevance for the conservation of the islands is unquestionable, since they are the epicenter of human activities that affect natural ecosystems. The different human activities carried out in these areas have created a matrix of environmental changes that need to be understood to improve the management of protected areas in Galapagos and elsewhere. In this chapter, some preliminary data from my current study in San Cristobal are examined to evaluate the effects of land use and climate change on nutrient dynamics, plant productivity, and diversity of animal communities, focusing on soil macroinvertebrates and terrestrial birds. In August 2011 and January 2012, soil and leaf samples were collected from 14 1 m² plots randomly selected in four sites that differ in their land use patterns: urban, organic agriculture, pasture and guava, and restoration with native plant species. These samples were analyzed to assess their nitrogen and carbon contents. In addition, the percentage of vegetation cover was estimated as a proxy for primary productivity and the diversity of soil macroinvertebrates in the plots. These data were complemented with bird censuses at three observation points in each site. Significant differences were found in all but one of the studied ecological variables among sites. Although preliminary, these results suggest that land use patterns have considerable effects on the structure and function of terrestrial ecosystems in the Galapagos. There is some evidence that pasture, in combination with guava, affect nutrient availability and that, at least in the rainy season, vegetation cover and macroinvertebrate diversity are partially and negatively related to the C/N ratio in soil. To my knowledge, this is the first study to analyze the effects of land use and climate on nutrient dynamics and community diversity in agricultural and urban systems in the Galapagos. Evidently, more data and analyses are needed to better understand the direction and extent of the impact of land use changes on island ecosystems. Similar analyses need to be carried out in protected areas with native vegetation at different altitudes and ecosystems, to be used as control sites. Further analyses should also include chrono-sequences of the studied variables in disturbed and restored areas of different ages, to have an insight into ecosystems’ resilience and the impact of current climate change. These preliminary findings and future research ideas may trigger more research on the impact of human activities on terrestrial ecosystems in the Galapagos.

Appendix A. Appendix 1. List of bird species recorded in each study site

Scientific name	Urban	Organic agriculture	Pasture and guava	Restoration
Crotophaga ani	X	X	X	X
Nesomimus melanotis	X	X	X	X
Dendroica petechia	X	X	X	X
Certhidea olivacea		X	X	X
Geospiza fortis	X	X	X	X
Geospiza fuliginosa	X	X	X	X
Platyspiza crassirostris		X	X	X
Camarhynchus pallidus		X	X	X
Camarhynchus parvulus		X		X
Myiarchus magnirostris	X
Bubulcus ibis			X	X