Subject
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Petroleum
145
Wilderness areas
144
Recreation
138
Ecosystems
137
Policy
134
Reforestation
134
Geochemistry
133
Geologic maps
133
Measurement
128
Minerals
128
Environment
125
Wetlands
123
Habitats
121
Field trips
120
Soils
120
Birds
119
Forest resources
119
Emissions
118
Environmental protection
118
Coal mining
115
Education
111
Wildlife conservation
111
Endangered species
110
Harvesting
110
Markets
110
Insects
109
Spruce
109
Regulations
106
Forest insects
105
Mines
105
Forest pests
103
Conifers
102
Energy
98
Evaluation
98
Analysis
96
Classification
96
Forest fires
96
Industrial minerals
96
Public opinion
96
Resource management
96
Mineralogy
95
Structural geology
95
Mineral exploration
94
Protected areas
94
Biodiversity
93
Balsam fir
92
Tidal power
91
Standards
90
Forest soils
89
Greenhouse gases
89
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