import pandas as pd
def assess_health(field_id):
obs = pd.read_sql("SELECT * FROM field_observations WHERE field_id = ?", field_id)
score = 100
for _, row in obs.iterrows():
if row['stress_level'] > 7: score -= 15
elif row['stress_level'] > 4: score -= 5
if row['pest_count'] > 10: score -= 20
return max(score, 0)