Plant Family-Specific Impacts of Petroleum Pollution on Biodiversity and Leaf Chlorophyll Content in the Amazon Rainforest of Ecuador

Abstract

In recent decades petroleum pollution in the tropical rainforest has caused significant environmental damage in vast areas of the Amazon region. At present the extent of this damage is not entirely clear. Little is known about the specific impacts of petroleum pollution on tropical vegetation. In a field expedition to the Ecuadorian Amazon over 1100 leaf samples were collected from tropical trees in polluted and unpolluted sites. Plant families were identified for 739 of the leaf samples and compared between sites. Plant biodiversity indices show a reduction of the plant biodiversity when the site was affected by petroleum pollution. In addition, reflectance and transmittance were measured with a field spectroradiometer for every leaf sample and leaf chlorophyll content was estimated using reflectance model inversion with the radiative tranfer model PROSPECT. Four of the 15 plant families that are most representative of the ecoregion (Melastomataceae, Fabaceae, Rubiaceae and Euphorbiaceae) had significantly lower leaf chlorophyll content in the polluted areas compared to the unpolluted areas. This suggests that these families are more sensitive to petroleum pollution. The polluted site is dominated by Melastomataceae and Rubiaceae, suggesting that these plant families are particularly competitive in the presence of pollution. This study provides evidence of a decrease of plant diversity and richness caused by petroleum pollution and of a plant family-specific response of leaf chlorophyll content to petroleum pollution in the Ecuadorian Amazon using information from field spectroscopy and radiative transfer modelling.

Application of PROSPECT for estimating total petroleum hydrocarbons in contaminated soils from leaf optical properties

“…The spectral signatures did however vary temporally and among species during the study. The variability among the five species highlighted natural differences in leaf anatomy and biochemistry and in sensitivity to TPH exposure [34,37,69]. When considering a single species, the spectral signatures also varied temporally with season changes, especially in the VIS and the red-edge regions.…”

“…The species established around industrial facilities are particularly tolerant to high levels of TPH [23,34]. This makes it difficult to detect and estimate TPH, as this implies being able to differentiate small alterations in pigment contents using leaf optical properties.…”

“…This is of major importance for detecting and estimating TPH, since not all pigments are affected in the same way by contamination [24][25]. PROSPECT could therefore be used for detecting and estimating TPH-induced changes in leaf pigment contents and consequently for determining the level of soil contamination [23,34].…”

Toward Quantifying Oil Contamination in Vegetated Areas Using Very High Spatial and Spectral Resolution Imagery

“…Below a certain concentration, oil no longer alters leaf pigment and water contents, so soil contamination becomes very difficult to detect using vegetation reflectance [21,28,30]. This detection limit strongly depends on the sensitivity of the species, and is higher for oil-tolerant species [20,33,38,89]. Thus, the closer the level of contamination to this limit, the less accurate the classification.…”

“…Species established around industrial oil facilities are naturally tolerant to soil contamination and difficult to distinguish from healthy vegetation [33,34]. It is, therefore, challenging to develop methods for detecting and quantifying TPH adapted to these species and intended to be applied to airborne and satellite hyperspectral images.…”