  In this paper, we consider a Fisher-KPP equation with an advection term and
two free boundaries, which models the behavior of an invasive species in one
dimension space. When spreading happens (that is, the solution converges to a
positive constant), we use phase plane analysis and upper/lower solutions to
prove that the rightward and leftward asymptotic spreading speeds exist, both
are positive constants. Moreover, one of them is bigger and the other is
smaller than the spreading speed in the corresponding problem without advection
term.
