Let F be a totally real number field and A a modular GL 2 -type abelian variety over F . Let K/F be a CM quadratic extension. Let χ be a class group character over K such that the Rankin-Selberg convolution L(s, A, χ) is self-dual with root number −1. We show that the number of class group characters χ with bounded ramification such that L ′ (1, A, χ) = 0 increases with the absolute value of the discriminant of K.We also consider a rather general rank zero situation. Let π be a cuspidal cohomological automorphic representation over GL 2 (A F ). Let χ be a Hecke character over K such that the Rankin-Selberg convolution L(s, π, χ) is self-dual with root number 1. We show that the number of Hecke characters χ with fixed ∞-type and bounded ramification such that L(1/2, π, χ) = 0 increases with the absolute value of the discriminant of K.The Gross-Zagier formula and the Waldspurger formula relate the question to horizontal nonvanishing of Heegner points and toric periods, respectively. For both situations, the strategy is geometric relying on the Zariski density of CM points on self-products of a quaternionic Shimura variety. The recent result [29, 34, 1] on the André-Oort conjecture is accordingly fundamental to the approach.